Inkjet recording ink and inkjet recording method

ABSTRACT

An object of the present invention is to provide an inkjet recording ink ensuring (1) excellent weather resistance (image preservability), (2) less blurring of image drawn and (3) high ejection stability. This object of the present invention can be attained by an inkjet recording ink, including an aqueous medium having dissolved therein at least two water soluble coloring materials sharing one spectral absorption region selected from a region of 500 to 580 nm and a region of 580 to 600 nm as the main absorption region in the aqueous medium.

TECHNICAL FIELD

The present invention relates to an inkjet recording ink and a recordingmethod using the ink, more specifically, the present invention relatesto an inkjet recording magenta ink ensuring excellent preservability ofrecorded image, less color bleeding of drawn image and excellent inkejection stability.

BACKGROUND ART

Accompanying recent popularization of computers, an inkjet printer iswidely used for printing letters or drawing an image on paper, film,cloth or the like not only at offices but also at homes.

The inkjet recording method includes a system of jetting out a liquiddroplet by applying a pressure from a piezoelectric element, a system ofjetting out a liquid droplet by generating a bubble in the ink underheat, a system of using an ultrasonic wave, and a system of jetting outa liquid droplet by suction using an electrostatic force. The inkjetrecording ink used therefor includes an aqueous ink, an oily ink and asolid (fusion-type) ink.

Among these inks, an aqueous ink is relatively superior to oily ink orsolid (fusion-type) ink in view of possibility of satisfying all ofproduction, handleability, odor, safety and the like and therefore, ispredominating as the inkjet recording ink at present.

The coloring material used in such an inkjet recording ink is requiredto have high solubility in a solvent (ink medium), enable high-densityrecording, provide good color hue, exhibit excellent fastness to light,heat, air, water and chemicals, ensure good fixing to an image-receivingmaterial and less bleeding, give an ink having excellent storability,have high purity and no toxicity, and be available at a low cost.However, although various dyes and pigments for use in inkjet recordinghave been already proposed and are actually used, a coloring materialsatisfying all of the requirements described above is not yet found outat present.

Conventionally well-known dyes and pigments such as coloring materialhaving a color index (C.I.) number can hardly satisfy all of thosevarious properties required of the inkjet recording ink.

As for the dye capable of improving the fastness, azo dyes derived froman aromatic amine and a 5-membered heterocyclic amine have been proposedin Patent Document 1. However, these dyes have a problem of bad colorreproducibility due to undesirable color hue present in the yellow andcyan regions. Patent Documents 2 and 3 are disclosing an inkjetrecording ink with an attempt to enhance the light fastness. However, inuse as a water-soluble ink, the coloring materials used in these patentpublications are insufficient in the solubility in water. Also, whenused as a water-soluble ink for inkjet recording, there arises a problemin the fastness to humidity and heat.

In order to solve these problems, compounds and ink compositionsdescribed in Patent Document 4 have been proposed. Furthermore, aninkjet recording ink using a pyrazolylaniline azo dye for improving thecolor hue and light fastness is described (Patent Document 5). However,these inkjet recording inks are still insufficient in the fastness ofimage output.

In addition to the image preservability, more reduction in the blurringof image is recently demanded accompanying requirement for a highlyrefined inkjet image. In preparing an ink, when only water is used, thepenetrability into a medium is bad and the image is not fixed in manycases. Also, the liquid properties necessary for hitting as an ink areoften not satisfied. For solving these problems, a technique of using awater-miscible high boiling point organic solvent as auxiliary solventand using a nonionic surfactant is commonly employed in this field.However, the formulation of preparing an ink containing an auxiliarysolvent and a surfactant for this purpose has a problem that blurring ofthe image drawn increases particularly under high-humidity conditions.

Out of those various properties required of the inkjet recording ink, itis not yet attained to sufficiently satisfy both excellent imagepreservability against light, heat and high humidity and less blurringof image drawn, and realization thereof is demanded on the market.

[List of Patent Documents as Background Art]

The above-described documents as the background art are as follows.

[Patent Document 1]

JP-A-55-1.61856 (the term “JP-A” as used herein means an “unexaminedpublished Japanese patent application”)

[Patent Document 2] JP-A-61-36362

[Patent Document 3] JP-A-2-212566

[Patent Document 4]

JP-T-11-504958 (the term “JP-T” as used herein means a “publishedJapanese translation of a PCT patent application”)

[Patent Document 5]

Japanese Patent Application No. 2000-80733

An object of the present invention is to solve the problems of inkjetrecording ink described above in the item of Background Art, morespecifically, to provide an inkjet recording ink ensuring 1) excellentweather resistance (image preservability), 2) less blurring of imagedrawn and 3) high ejection stability.

DISCLOSURE OF THE INVENTION

The object of the present invention can be attained by the inkjetrecording ink or ink set described in the following (1) to (15). Theseinkjet recording ink and ink set are used for inkjet recording accordingto the method described in (16) to (20) below. In particular, the effectof the present invention is remarkably brought out when the imagerecording is performed on the image-receiving layer of the imagerecording material described in (19) or (20).

(1) An inkjet recording ink, which may comprise multiple aqueousmediums, comprising an aqueous medium having dissolved or dispersedtherein at least two coloring materials sharing one spectral absorptionregion selected from a region of 500 to 580 nm and a region of 580 to680 nm as the main absorption region in the aqueous medium.

(2) The inkjet recording ink as described in (1) above, wherein at leasttwo coloring materials sharing one spectral absorption region selectedfrom a region of 500 to 580 nm and a region of 580 to 680 nm as the mainabsorption region in the aqueous medium are dissolved or dispersed in asingle aqueous medium.

(3) The inkjet recording ink as described in (1) above, wherein at leasttwo coloring materials sharing one spectral absorption region selectedfrom a region of 500 to 580 nm and a region of 580 to 680 nm as the mainabsorption region in the aqueous medium are separately dissolved ordispersed in multiple aqueous mediums.

(4) The inkjet recording ink as described in any one of (1) to (3)above, wherein one of the at least two coloring materials is a pigmentinsoluble in water and dispersed in the aqueous medium.

(5) The inkjet recording ink as described in any one of (1) to (4)above, wherein the main absorption region shared by at least twocoloring materials in the aqueous medium is the region of 500 to 580 nm.

(6) The inkjet recording ink as described in (5) above, wherein at leastone of coloring materials sharing the region of 500 to 580 nm as themain absorption region is an azo dye having a chromophore represented bythe formula: (heterocyclic ring A)-N═N-(heterocyclic ring B), providedthat the heterocyclic ring A and the heterocyclic B may have the samestructure.

(7) The inkjet recording ink as described in (6) above, wherein the azodye having a chromophore represented by the formula: (heterocyclic ringA)-N═N-(heterocyclic ring B), is a coloring material having an oxidationpotential nobler than 0.7 V (vs SCE).

(8) The inkjet recording ink as described in any one of (4) to (7)above, wherein the azo dye is a dye represented by the following formula(1):

wherein A represents a 5-membered heterocyclic group;

B¹ and B² each represents ═CR¹— or —CR²═ or either one of B¹ and B²represents a nitrogen atom and the other represents ═CR¹— or —CR²═;

R⁵ and R⁶ each independently represents a hydrogen atom or asubstituent, the substituent is an aliphatic group, an aromatic group, aheterocyclic group, an acyl group, an alkoxycarbonyl group, anaryloxycarbonyl group, a carbamoyl group, an alkylsulfonyl group, anarylsulfonyl group or a sulfamoyl group, and the hydrogen atom of eachsubstituent may be substituted;

G, R¹ and R² each independently represents a hydrogen atom or asubstituent, the substituent is a halogen atom, an aliphatic group, anaromatic group, a heterocyclic group, a cyano group, a carboxyl group, acarbamoyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, aheterocyclic oxycarbonyl group, an acyl group, a hydroxy group, analkoxy group, an aryloxy group, a heterocyclic oxy group, a silyloxygroup, an acyloxy group, a carbamoyloxy group, an alkoxycarbonyloxygroup, an aryloxycarbonyloxy group, an amino group, an acylamino group,a ureido group, a sulfamoylamino group, an alkoxycarbonylamino group, anaryloxycarbonylamino group, an alkylsulfonylamino group, anarylsulfonylamino group, a heterocyclic sulfonylamino group, a nitrogroup, an alkylthio group, an arylthio group, a heterocyclic thio group,an alkylsulfonyl group, an arylsulfonyl group, a heterocyclic sulfonylgroup, an alkylsulfinyl group, an arylsulfinyl group, a heterocyclicsulfinyl group, a sulfamoyl group or a sulfo group, and the hydrogenatom of each substituent may be substituted; and

R¹ and R⁵, or R⁵ and R⁶ may combine to form a 5- or 6-membered ring.

(9) The inkjet recording ink as described in (8) above, wherein the atleast two coloring materials sharing the main absorption region both arethe dye represented by formula (1).

(10) The inkjet recording ink as described in any one of (1) to (4)above, wherein the main absorption region shared by at least twocoloring materials in the aqueous medium is the region of 580 to 680 nm.

(11) The inkjet recording ink as described in (10) above, wherein atleast one of coloring materials sharing the region of 580 to 680 nm asthe main absorption region is a dye represented by the following formula(I):

wherein X₁, X₂, X₃ and X₄ each independently represents —SO-Z, —SO₂-Z,—SO₂NR₁R₂, a sulfo group, —CONR₁R₂ or —CO₂R₁ (wherein Z represents asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedcycloalkyl group, a substituted or unsubstituted alkenyl group, asubstituted or unsubstituted aralkyl group, a substituted orunsubstituted aryl group, or a substituted or unsubstituted heterocyclicgroup, and R₁ and R₂ each independently represents a hydrogen atom, asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedcycloalkyl group, a substituted or unsubstituted alkenyl group, asubstituted or unsubstituted aralkyl group, a substituted orunsubstituted aryl group, or a substituted or unsubstituted heterocyclicgroup, provided that when a plurality of Zs are present, these may bethe same or different),

Y₁, Y₂, Y₃ and Y₄ each independently represents a monovalentsubstituent,

provided that when a plurality of X₁s, X₂s, X₃s, X₄s, Y₁s, Y₂s, Y₃s orY₄s are present, these may be the same or different,

a₁ to a₄ and b₁ to b₄ represent the number of substituents X₁ to X₄ andY₁ to Y₄, respectively, a₁ to a₄ each independently represents aninteger of 0 to 4 but all are not 0 at the same time, b₁ to b₄ eachindependently represents an integer of 0 to 4, and

M represents a hydrogen atom, a metal atom or an oxide, hydroxide orhalide thereof.

(12) The inkjet recording ink as described in (11) above, wherein thedye represented by formula (I) is a dye represented by the followingformula (II):

wherein X₁₁ to X₁₄, Y₁₁ to Y₁₈ and M have the same meanings as X₁ to X₄,Y₁ to Y₄ and M in formula (I), respectively, and

a₁₁ to a₁₄ each independently represents an integer of 1 or 2.

(13) The inkjet recording ink as described in any one of (10) to (12)above, wherein at least one dye represented by formula (I) and at leastone dye having a structure different from the above-described dye aredissolved or dispersed in an aqueous medium.

(14) The inkjet recording ink as described in any one of (10) to (13)above, wherein at least two dyes represented by formula (I) aredissolved or dispersed in an aqueous medium.

(15) The inkjet recording ink as described in any one of (10) to (14)above, wherein the dye represented by formula (I) is a coloring materialhaving an oxidation potential nobler than 0.7 V (vs SCE).

(16) An inkjet recording method comprising using the ink described inany one of (1) to (15) above.

(17) The inkjet recording method as described in (16) above, which usesan ink set comprising multiple aqueous mediums having separatelydissolved or dispersed therein at least two coloring materials sharingone spectral absorption region selected from a region of 500 to 580 nmand a region of 580 to 680 nm as the main absorption region in theaqueous medium, wherein an inkjet recording ink comprising an aqueousmedium having dissolved or dispersed therein at least one dyerepresented by formula (I) and an inkjet recording ink comprising anaqueous medium having dissolved or dispersed therein at least onecoloring material differing in the structure from the above-describeddye and sharing the main absorption region with that dye are used as acombined set.

(18) The inkjet recording method as described in (16) above, which usesan ink comprising an aqueous medium having dissolved or dispersedtherein at least two coloring materials sharing one spectral absorptionregion selected from a region of 500 to 580 nm and a region of 580 to680 nm as the main absorption region in the aqueous medium, wherein inthe inkjet recording ink used, at least one dye represented by formula(1) and at least one dye differing in the structure from theabove-described dye and sharing the main absorption region with that dyeare dissolved or dispersed in the same aqueous medium.

(19) The inkjet recording method as described in any one of (16) to (18)above, wherein an image is recorded by ejecting ink droplets accordingto recording signals on an image-receiving material comprising a supporthaving thereon an image-receiving layer containing an inorganic whitepigment particle.

(20) The inkjet recording method as described in (19) above, wherein theimage-receiving layer comprises an inorganic white pigment particle andat least one aqueous binder selected from polyvinyl alcohol,silanol-modified polyvinyl alcohol, starch, cationized starch, gelatin,carboxyalkyl cellulose, casein and polyvinylpyrrolidone.

In other words, the present invention, which is an ink using an aqueousmedium, is based on the finding that in an ink having a main absorptionregion of 500 to 580 nm, namely, an ink generally called a magenta ink,and in an ink having a main absorption region of 580 to 680 nm, namely,an ink generally called a cyan ink, when at least two coloring materialsare used in each ink by dissolving or dispersing them, the imagepreservability, the color bleeding of image drawn and the ejectionstability all are improved to a level unachievable by, for example,increasing the amount of only one coloring material and the object ofthe present invention can be attained.

Those at least two coloring materials are coloring materials used in anaqueous medium and as long as the coloring materials are sharing themain absorption region of 500 to 580 nm or of 580 to 600 nm in themedium, the effect of the present invention can be brought out.Moreover, not only in the case of an ink where at least two coloringmaterials are dissolved or dispersed in a single aqueous medium but alsoin the case of an ink set where two coloring materials are separatelydissolved or dispersed in multiple aqueous mediums, the objective effectcan be obtained (in the present invention, if arises nomisunderstanding, the term “ink” is used including the ink set havingsuch a meaning). That is, the effect of the present invention isconsidered to come out when the recorded image is constituted by theabove-described two or more coloring materials.

In order to bring out excellent image preservability, at least one ofthose two coloring materials preferably has an oxidation potentialnobler than 0.7 V (vs SCE). When at least one coloring material havingsuch a high oxidation potential is present, the image obtained bycombining it with another coloring material having the same mainabsorption region can have fastness and the image preservability isenhanced.

One of two coloring materials may be a pigment or sparingly soluble dyewhich is insoluble in an aqueous ink medium and added to the compositionby emulsion-dispersion.

The coloring material having a main absorption region of 500 to 580 nmand the coloring material having a main absorption region of 580 to 680nm, which are particularly preferred in the present invention, are anazo dye with the nitrogen atom of the azo group being directly bonded bya heterocyclic group having a specific structure, and a phthalocyaninedye having a specific substituent structure, respectively.

BEST MODE FOR CARRYING OUT THE INVENTION

Specific embodiments of the present invention are described in detailbelow.

In the present invention, the term “coloring material” is used whencollectively indicating a dye and a pigment.

<Coloring Materials Sharing Main Absorption Region of 500 to 580 nm>

In order to satisfy the objective properties required of the inkjetrecording ink of the present invention, that is, excellent weatherresistance, ensured color hue, high ejection stability and no defect inview of water resistance and image quality, as for the magenta ink, anink having properties specified in (1) to (9) above is used for theimage recording. Accordingly, these properties of the magenta dye aredescribed below.

In the magenta ink used for the inkjet recording ink of the presentinvention, a magenta dye selected from azo dyes is dissolved ordispersed in an aqueous medium and the dye is fundamentallycharacterized in that the absorption maximum in the aqueous medium ispresent in the spectral region of 500 to 580 nm and the oxidationpotential is nobler than 0.7 V (vs SCE).

The first preferred structural feature of this azo dye is that the dyehas a chromophore represented by the formula: (heterocyclic ringA)-N═N-(heterocyclic ring B). In this case, the heterocyclic rings A andB may have the same structure. Specifically, the heterocyclic rings Aand B each is a 5- or 6-membered heterocyclic ring selected frompyrazole, imidazole, triazole, oxazole, thiazole, selenazole, pyridone,pyrazine, pyrimidine and pyridine. These are specifically described, forexample, in Japanese Patent Application Nos. 2000-15853 and 2001-15614,JP-A-2002-309116 and Japanese Patent Application No. 2001-195014.

The second preferred structural feature of the azo dye is that anaromatic nitrogen-containing 6-membered heterocyclic ring is bonded as acoupling component directly to at least one side of the azo group.Specific examples thereof are described in 2001-110457.

The third preferred structural feature is that the auxochrome has anaromatic ring amino group or heterocyclic amino group structure,specifically, an anilino group or a heterylamino group.

The fourth preferred structural feature is that the dye has a stericstructure. This is specifically described in Japanese Patent ApplicationNo. 2002-12015.

Among these preferred structural features of the azo dye, the dye mostpreferred for achieving the object of the present invention is a dyerepresented by the following formula (1):

wherein

A represents a 5-membered heterocyclic group;

B¹ and B² each represents ═CR¹— or —CR²═ or either one of B¹ and B²represents a nitrogen atom and the other represents ═CR¹— or —CR²═;

R⁵ and R⁶ each independently represents a hydrogen atom or asubstituent, the substituent is an aliphatic group, an aromatic group, aheterocyclic group, an acyl group, an alkoxycarbonyl group, anaryloxycarbonyl group, a carbamoyl group, an alkylsulfonyl group, anarylsulfonyl group or a sulfamoyl group, and the hydrogen atom of eachsubstituent may be substituted;

G, R¹ and R² each independently represents a hydrogen atom or asubstituent, the substituent is a halogen atom, an aliphatic group, anaromatic group, a heterocyclic group, a cyano group, a carboxyl group, acarbamoyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, aheterocyclic oxycarbonyl group, an acyl group, a hydroxy group, analkoxy group, an aryloxy group, a heterocyclic oxy group, a silyloxygroup, an acyloxy group, a carbamoyloxy group, an alkoxycarbonyloxygroup, an aryloxycarbonyloxy group, an amino group, an acylamino group,a ureido group, a sulfamoylamino group, an alkoxycarbonylamino group, anaryloxycarbonylamino group, an alkylsulfonylamino group, anarylsulfonylamino group, a heterocyclic sulfonylamino group, a nitrogroup, an alkylthio group, an arylthio group, a heterocyclic thio group,an alkylsulfonyl group, an arylsulfonyl group, a heterocyclic sulfonylgroup, an alkylsulfinyl group, an arylsulfinyl group, a heterocyclicsulfinyl group, a sulfamoyl group or a sulfo group, and the hydrogenatom of each substituent may be substituted; and

R¹ and R⁵, or R⁵ and R⁶ may combine to form a 5- or 6-membered ring.

The dye of formula (1) is described in more detail.

In formula (1), A represents a 5-membered heterocyclic group. Examplesof the heteroatom of the heterocyclic ring include N, O and S. A ispreferably a nitrogen-containing 5-membered heterocyclic ring and theheterocyclic ring may be condensed with an aliphatic ring, an aromaticring or another heterocyclic ring. Preferred examples of theheterocyclic ring represented by A include a pyrazole ring, an imidazolering, a thiazole ring, an isothiazole ring, a thiadiazole ring, abenzothiazole ring, a benzoxazole ring and a benzisothiazole ring. Eachheterocyclic group may further have a substituent. Among these rings,more preferred are a pyrazole ring, an imidazole ring, an isothiazolering, a thiadiazole ring and a benzothiazole ring represented by thefollowing formulae (a) to (f):

wherein R⁷ to R²⁰ each represents the same substituent as G, R¹ and R²in formula (1).

Among formulae (a) to (f), preferred are a pyrazole ring and anisothiazole ring represented by formulae (a) and (b), and most preferredis a pyrazole ring represented by formula (a).

In formula (1) B¹ and B² each represents ═CR¹— or —CR²═ or either one ofB¹ and B² represents a nitrogen atom and the other represents ═CR¹— or—CR²═. B¹ and B² each preferably represents ═CR¹— or —CR²═.

R⁵ and R⁶ each independently represents a hydrogen atom or asubstituent, the substituent is an aliphatic group, an aromatic group, aheterocyclic group, an acyl group, an alkoxycarbonyl group, anaryloxycarbonyl group, a carbamoyl group, an alkylsulfonyl group, anarylsulfonyl group or a sulfamoyl group, and the hydrogen atom of eachsubstituent may be substituted.

R⁵ and R⁶ each is preferably a hydrogen atom, an aliphatic group, anaromatic group, a heterocyclic group, an acyl group, an alkylsulfonylgroup or an arylsulfonyl group, more preferably a hydrogen atom, anaromatic group, a heterocyclic group, an acyl group, an alkylsulfonylgroup or an arylsulfonyl group, and most preferably a hydrogen atom, anaryl group or a heterocyclic group, and the hydrogen atom of eachsubstituent may be substituted, but R⁵ and R⁶ are not a hydrogen atom atthe same time.

G, R¹ and R² each independently represents a hydrogen atom or asubstituent, the substituent is a halogen atom, an aliphatic group, anaromatic group, a heterocyclic group, a cyano group, a carboxyl group, acarbamoyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, aheterocyclic oxycarbonyl group, an acyl group, a hydroxy group, analkoxy group, an aryloxy group, a heterocyclic oxy group, a silyloxygroup, an acyloxy group, a carbamoyloxy group, an alkoxycarbonyloxygroup, an aryloxycarbonyloxy group, an amino group, an acylamino group,a ureido group, a sulfamoylamino group, an alkoxycarbonylamino group, anaryloxycarbonylamino group, an alkylsulfonylamino group, anarylsulfonylamino group, a heterocyclic sulfonylamino group, a nitrogroup, an alkylthio group, an arylthio group, a heterocyclic thio group,an alkylsulfonyl group, an arylsulfonyl group, a heterocyclic sulfonylgroup, an alkylsulfinyl group, an arylsulfinyl group, a heterocyclicsulfinyl group, a sulfamoyl group or a sulfo group, and the hydrogenatom of each substituent may be substituted.

G is preferably a hydrogen atom, a halogen atom, an aliphatic group, anaromatic group, a hydroxy group, an alkoxy group, an aryloxy group, anacyloxy group, a heterocyclic oxy group, an amino group, an acylaminogroup, a ureido group, a sulfamoylamino group, an alkoxycarbonylaminogroup, an aryloxycarbonylamino group, an alkylthio group, an arylthiogroup or a heterocyclic thio group, more preferably a hydrogen atom, ahalogen atom, an alkyl group, a hydroxy group, an alkoxy group, anaryloxy group, an acyloxy group, an amino group or an acylamino group,and most preferably a hydrogen atom, an amino group (preferably ananilino group) or an acylamino group, and the hydrogen atom of eachsubstituent may be substituted.

R¹ and R² each is preferably a hydrogen atom, an alkyl group, a halogenatom, an alkoxycarbonyl group, a carboxyl group, a carbamoyl group, ahydroxy group, an alkoxy group or a cyano group, and the hydrogen atomof each substituent may be substituted.

R¹ and R⁵, or R⁵ and R⁶ may combine to form a 5- or 6-membered ring.

When A has a substituent or when the substituent R¹, R², R⁵, R⁶ or Gfurther has a substituent, examples of the substituent include thesubstituents described above for G, R¹ and R².

In the case where the dye of the present invention is a water-solubledye, the dye preferably further has an ionic hydrophilic group as asubstituent on any position of A, R¹, R², R⁵, R⁶ and G. Examples of theionic hydrophilic group as a substituent include a sulfo group, acarboxyl group, a phosphono group and a quaternary ammonium group. Amongthese ionic hydrophilic groups, preferred are a carboxyl group, aphosphono group and a sulfo group, more preferred are a carboxyl groupand a sulfo group. The carboxyl group, the phosphono group and the sulfogroup each may be in a salt state and examples of the counter ion forforming the salt include ammonium ion, alkali metal ions (e.g., lithiumion, sodium ion, potassium ion) and organic cations (e.g.,tetramethylammonium ion, tetramethylguanidium ion,tetramethylphosphonium).

The terms (substituents) used in the present invention are describedbelow. These terms each is common among different symbols in formula (1)and also in formula (1a) shown later.

The halogen atom includes a fluorine atom, a chlorine atom and a bromineatom.

The aliphatic group means an alkyl group, a substituted alkyl group, analkenyl group, a substituted alkenyl group, an alkynyl group, asubstituted alkynyl group, an aralkyl group and a substituted aralkylgroup. The “substituted” used for a “substituted alkyl group” and thelike in the present invention means that the hydrogen atom present in an“alkyl group” or the like is substituted, for example, by a substituentdescribed above for G, R¹ and R².

The aliphatic group may be branched or may form a ring. The number ofcarbon atoms in the aliphatic group is preferably from 1 to 20, morepreferably from 1 to 16. The aryl moiety in the aralkyl group and in thesubstituted aralkyl group is preferably a phenyl group or a naphthylgroup, more preferably a phenyl group. Examples of the aliphatic groupinclude a methyl group, an ethyl group, a butyl group, an isopropylgroup, a tert-butyl group, a hydroxyethyl group, a methoxyethyl group, acyanoethyl group, a trifluoromethyl group, a 3-sulfopropyl group, a4-sulfobutyl group, a cyclohexyl group, a benzyl group, a 2-phenethylgroup, a vinyl group and an allyl group.

The aromatic group means an aryl group and a substituted aryl group. Thearyl group is preferably a phenyl group or a naphthyl group, morepreferably a phenyl group. The number of carbon atoms in the aromaticgroup is preferably from 6 to 20, more preferably from 6 to 16.

Examples of the aromatic group include a phenyl group, a p-tolyl group,a p-methoxyphenyl group, an o-chlorophenyl group and anm-(3-sulfopropylamino)phenyl group.

The heterocyclic group includes a substituted heterocyclic group. In theheterocyclic group, the heterocyclic ring may be condensed with analiphatic ring, an aromatic ring or another heterocyclic ring. Theheterocyclic group is preferably a 5- or 6-membered heterocyclic group.Examples of the substituent of the substituted heterocyclic groupinclude an aliphatic group, a halogen atom, an alkylsulfonyl group, anarylsulfonyl group, an acyl group, an acylamino group, a sulfamoylgroup, a carbamoyl group and an ionic hydrophilic group. Examples of theheterocyclic group include a 2-pyridyl group, a 2-thienyl group, a2-thiazolyl group, a 2-benzothiazolyl group, a 2-benzoxazolyl group anda 2-furyl group.

The carbamoyl group includes a substituted carbamoyl group. Examples ofthe substituent therefor include an alkyl group. Examples of thecarbamoyl group include a methylcarbamoyl group and a dimethylcarbamoylgroup.

The alkoxycarbonyl group includes a substituted alkoxycarbonyl group.The alkoxycarbonyl group is preferably an alkoxycarbonyl group havingfrom 2 to 20 carbon atoms. Examples of the substituent of thesubstituted alkoxycarbonyl group include an ionic hydrophilic group.Examples of the alkoxycarbonyl group include a methoxycarbonyl group andan ethoxycarbonyl group.

The aryloxycarbonyl group includes a substituted aryloxycarbonyl group.The aryloxycarbonyl group is preferably an aryloxycarbonyl group havingfrom 7 to 20 carbon atoms. Examples of the substituent of thesubstituted aryloxycarbonyl group include an ionic hydrophilic group.Examples of the aryloxycarbonyl group include a phenoxycarbonyl group.

The heterocyclic oxycarbonyl group includes a substituted heterocyclicoxycarbonyl group. Examples of the heterocyclic ring include theheterocyclic rings described above for the heterocyclic group. Theheterocyclic oxycarbonyl group is preferably a heterocyclic oxycarbonylgroup having from 2 to 20 carbon atoms.

Examples of the substituent of the substituted heterocyclic oxycarbonylgroup include an ionic hydrophilic group. Examples of the heterocyclicoxycarbonyl group include a 2-pyridyloxycarbonyl group.

The acyl group includes a substituted acyl group. The acyl group ispreferably an acyl group having from 1 to 20 carbon atoms. Examples ofthe substituent of the substituted acyl group include an ionichydrophilic group. Examples of the acyl group include an acetyl groupand a benzoyl group.

The alkoxy group includes a substituted alkoxy group. The alkoxy groupis preferably an alkoxy group having from 1 to 20 carbon atoms. Examplesof the substituent of the substituted alkoxy group include an alkoxygroup, a hydroxyl group and an ionic hydrophilic group. Examples of thealkoxy group include a methoxy group, an ethoxy group, an isopropoxygroup, a methoxyethoxy group, a hydroxyethoxy group and a3-carboxypropoxy group.

The aryloxy group includes a substituted aryloxy group. The aryloxygroup is preferably an aryloxy group having from 6 to 20 carbon atoms.Examples of the substituent of the substituted aryloxy group include analkoxy group and an ionic hydrophilic group. Examples of the aryloxygroup include a phenoxy group, a p-methoxyphenoxy group and ano-methoxyphenoxy group.

The heterocyclic oxy group includes a substituted heterocyclic oxygroup. Examples of the heterocyclic ring include the heterocyclic ringsdescribed above for the heterocyclic group. The heterocyclic oxy groupis preferably a heterocyclic oxy group having from 2 to 20 carbon atoms.Examples of the substituent of the substituted heterocyclic oxy groupinclude an alkyl group, an alkoxy group and an ionic hydrophilic group.Examples of the heterocyclic oxy group include a 3-pyridyloxy group anda 3-thienyloxy group.

The silyloxy group is preferably a silyloxy group substituted by analiphatic or aromatic group having from 1 to 20 carbon atoms. Examplesof the silyloxy group include a trimethylsilyloxy group and adiphenylmethylsilyloxy group.

The acyloxy group includes a substituted acyloxy group. The acyloxygroup is preferably an acyloxy group having from 1 to 20 carbon atoms.Examples of the substituent of the substituted acyloxy group include anionic hydrophilic group. Examples of the acyloxy group include anacetoxy group and a benzoyloxy group.

The carbamoyloxy group includes a substituted carbamoyloxy group.Examples of the substituent therefor include an alkyl group. Examples ofthe carbamoyloxy group include an N-methylcarbamoyloxy group.

The alkoxycarbonyloxy group includes a substituted alkoxycarbonyloxygroup. The alkoxycarbonyloxy group is preferably an alkoxycarbonyloxygroup having from 2 to 20 carbon atoms. Examples of thealkoxycarbonyloxy group include a methoxycarbonyloxy group and anisopropoxy-carbonyloxy group.

The aryloxycarbonyloxy group includes a substituted aryloxycarbonyloxygroup. The aryloxycarbonyloxy group is preferably an aryloxycarbonyloxygroup having from 7 to 20 carbon atoms. Examples of thearyloxycarbonyloxy group include a phenoxycarbonyloxy group.

The amino group includes a substituted amino group. Examples of thesubstituent therefor include an alkyl group, an aryl group and aheterocyclic group, and the alkyl group, the aryl group and theheterocyclic group each may further have a substituent. The alkylaminogroup includes a substituted alkylamino group. The alkylamino group ispreferably an alkylamino group having from 1 to 20 carbon atoms.Examples of the substituent of the substituted alkylamino group includean ionic hydrophilic group. Examples of the alkylamino group include amethylamino group and a diethylamino group.

The arylamino group includes a substituted arylamino group. Thearylamino group is preferably an arylamino group having from 6 to 20carbon atoms. Examples of the substituent of the substituted arylaminogroup include a halogen atom and an ionic hydrophilic group. Examples ofthe arylamino group include a phenylamino group and a2-chlorophenylamino group.

The heterocyclic amino group includes a substituted heterocyclic aminogroup. Examples of the heterocyclic ring include the heterocyclic ringsdescribed above for the heterocyclic group. The heterocyclic amino groupis preferably a heterocyclic amino group having from 2 to 20 carbonatoms. Examples of the substituent of the substituted heterocyclic aminogroup include an alkyl group, a halogen atom and an ionic hydrophilicgroup.

The acylamino group includes a substituted acylamino group. Theacylamino group is preferably an acylamino group having from 2 to 20carbon atoms. Examples of the substituent of the substituted acylaminogroup include an ionic hydrophilic group. Examples of the acylaminogroup include an acetylamino group, a propionylamino group, abenzoylamino group, an N-phenylacetylamino group and a3,5-disulfobenzoylamino group.

The ureido group includes a substituted ureido group. The ureido groupis preferably a ureido group having from 1 to 20 carbon atoms. Examplesof the substituent of the substituted ureido group include an alkylgroup and an aryl group. Examples of the ureido group include a3-methylureido group, a 3,3-dimethylureido group and a 3-phenylureidogroup.

The sulfamoylamino group includes a substituted sulfamoylamino group.Examples of the substituent therefor include an alkyl group. Examples ofthe sulfamoylamino group include an N,N-dipropylsulfamoylamino group.

The alkoxycarbonylamino group includes a substituted alkoxycarbonylaminogroup. The alkoxycarbonylamino group is preferably analkoxycarbonylamino group having from 2 to 20 carbon atoms. Examples ofthe substituent of the substituted alkoxycarbonylamino group include anionic hydrophilic group. Examples of the alkoxycarbonylamino groupinclude an ethoxycarbonylamino group.

The aryloxycarbonylamino group includes a substitutedaryloxycarbonylamino group. The aryloxycarbonylamino group is preferablyan aryloxycarbonylamino group having from 7 to 20 carbon atoms. Examplesof the substituent of the substituted aryloxycarbonylamino group includean ionic hydrophilic group. Examples of the aryloxycarbonylamino groupinclude a phenoxycarbonylamino group.

The alkylsulfonylamino group and the arylsulfonylamino group include asubstituted alkylsulfonylamino group and a substituted arylsulfonylaminogroup, respectively. The alkylsulfonylamino group and thearylsulfonylamino group are preferably an alkylsulfonylamino grouphaving from 1 to 20 carbon atoms and an arylsulfonylamino group havingfrom 1 to 20 carbon atoms, respectively. Examples of the substituent ofthe substituted alkylsulfonylamino group and substitutedarylsulfonylamino group include an ionic hydrophilic group. Examples ofthe alkylsulfonylamino group and arylsulfonylamino group include amethylsufonylamino group, an N-phenyl-methylsulfonylamino group, aphenylsulfonylamino group and a 3-carboxyphenyl-sulfonylamino group.

The heterocyclic sulfonylamino group includes a substituted heterocyclicsulfonylamino group. Examples of the heterocyclic ring include theheterocyclic rings described above for the heterocyclic group. Theheterocyclic sulfonylamino group is preferably a heterocyclicsulfonylamino group having from 1 to 12 carbon atoms. Examples of thesubstituent of the substituted heterocyclic sulfonylamino group includean ionic hydrophilic group. Examples of the heterocyclic sulfonylaminogroup include a 2-thienylsulfonylamino group and a3-pyridylsulfonylamino group.

The alkylthio group, the arylthio group and the heterocyclic thio groupinclude a substituted alkylthio group, a substituted arylthio group anda substituted heterocyclic thio group, respectively. Examples of theheterocyclic ring include the heterocyclic rings described above for theheterocyclic group. The alkylthio group, the arylthio group and theheterocyclic thio group are preferably an alkylthio group having from 1to 20 carbon atoms, an arylthio group having from 1 to 20 carbon atomsand a heterocyclic thio group having from 1 to 20 carbon atoms,respectively. Examples of the substituent of the substituted alkylthiogroup, substituted arylthio group and substituted heterocyclic thiogroup include an ionic hydrophilic group. Examples of the alkylthiogroup, arylthio group and heterocyclic thio group include a methylthiogroup, a phenylthio group and a 2-pyridylthio group.

The alkylsulfonyl group and the arylsulfonyl group include a substitutedalkylsulfonyl group and a substituted arylsulfonyl group, respectively.Examples of the alkylsulfonyl group and arylsulfonyl group include amethylsulfonyl group and a phenylsulfonyl group.

The heterocyclic sulfonyl group includes a substituted heterocyclicsulfonyl group. Examples of the heterocyclic ring include theheterocyclic rings described above for the heterocyclic group. Theheterocyclic sulfonyl group is preferably a heterocyclic sulfonyl grouphaving from 1 to 20 carbon atoms. Examples of the substituent of thesubstituted heterocyclic sulfonyl group include an ionic hydrophilicgroup. Examples of the heterocyclic sulfonyl group include a2-thienylsulfonyl group and a 3-pyridylsulfonyl group.

The alkylsulfinyl group and the arylsulfinyl group include a substitutedalkylsulfinyl group and a substituted arylsulfinyl group, respectively.Examples of the alkylsulfinyl group and arylsulfinyl group include amethylsulfinyl group and a phenylsulfinyl group.

The heterocyclic sulfinyl group includes a substituted heterocyclicsulfinyl group. Examples of the heterocyclic ring include theheterocyclic rings described above for the heterocyclic group. Theheterocyclic sulfinyl group is preferably a heterocyclic sulfinyl grouphaving from 1 to 20 carbon atoms. Examples of the substituent of thesubstituted heterocyclic sulfinyl group include an ionic hydrophilicgroup. Examples of the heterocyclic sulfinyl group include a4-pyridylsulfinyl group.

The sulfamoyl group includes a substituted sulfamoyl group. Examples ofthe substituent therefor include an alkyl group. Examples of thesulfamoyl group include a dimethylsulfamoyl group and adi-(2-hydroxyethyl)sulfamoyl group.

Among the dyes represented by formula (1), particularly preferred is astructure represented by the following formula (1a):

In formula (1a), R¹, R², R⁵ and R⁶ have the same meanings as in formula(1).

R³ and R⁴ each independently represents a hydrogen atom or a substituentand the substituent is an aliphatic group, an aromatic group, aheterocyclic group, an acyl group, an alkoxycarbonyl group, anaryloxycarbonyl group, a carbamoyl group, an alkylsulfonyl group, anarylsulfonyl group or a sulfamoyl group. R³ and R⁴ each is preferably ahydrogen atom, an aromatic group, a heterocyclic group, an acyl group,an alkylsulfonyl group or an arylsulfonyl group, more preferably ahydrogen atom, an aromatic group or a heterocyclic group.

Z¹ represents an electron-withdrawing group having a Hammett'ssubstituent constant σp value of 0.20 or more. Z¹ is preferably anelectron-withdrawing group having σp value of 0.30 or more, morepreferably 0.45 or more, still more preferably 0.60 to more, but the σpvalue preferably does not exceed 1.0. Specific preferred examples ofthis substituent include electron-withdrawing substituents describedlater. Among those, preferred are an acyl group having from 2 to 20carbon atoms, an alkyloxycarbonyl group having from 2 to 20 carbonatoms, a nitro group, a cyano group, an alkylsulfonyl group having from1 to 20 carbon atoms, an arylsulfonyl group having from 6 to 20 carbonatoms, a carbamoyl group having from 1 to 20 carbon atoms and ahalogenated alkyl group having from 1 to 20 carbon atoms, more preferredare a cyano group, an alkylsulfonyl group having from 1 to 20 carbonatoms and an arylsulfonyl group having from 6 to 20 carbon atoms, andmost preferred is a cyano group.

Z² represents a hydrogen atom or a substituent and the substituent is analiphatic group, an aromatic group or a heterocyclic group. Z² ispreferably an aliphatic group, more preferably an alkyl group havingfrom 1 to 6 carbon atoms.

Q represents a hydrogen atom or a substituent and the substituent is analiphatic group, an aromatic group or a heterocyclic group. Q ispreferably a group comprising a nonmetallic atom group necessary forforming a 5-, 6-, 7- or 8-membered ring. The 5-, 6-, 7- or 8-memberedring may be substituted, may be a saturated ring or may have anunsaturated bond. Q is more preferably an aromatic group or aheterocyclic group. Preferred examples of the nonmetallic atom include anitrogen atom, an oxygen atom, a sulfur atom and a carbon atom. Specificexamples of the ring structure include a benzene ring, a cyclopentanering, a cyclohexane ring, a cycloheptane ring, a cyclooctane ring, acyclohexene ring, a pyridine ring, a pyrimidine ring, a pyrazine ring, apyridazine ring, a triazine ring, an imidazole ring, a benzimidazolering, an oxazole ring, a benzoxazole ring, a thiazole ring, abenzothiazole ring, an oxane ring, a sulfolane ring and a thiane ring.

The hydrogen atom of each substituent described in regard to formula(1a) may be substituted. Examples of the substituent include thesubstituents described in regard to formula (1), the groups described asexamples for G. R¹ and R², and ionic hydrophilic groups.

Here, the Hammett's substituent constant σp value used in the presentinvention is described. The Hammett's rule is an empirical ruleadvocated by L. P. Hammett in 1935 so as to quantitatively discuss theeffect of substituent on the reaction or equilibrium of benzenederivatives and its propriety is widely admitted at present. Thesubstituent constant determined by the Hammett's rule includes a σpvalue and a σm value and these values can be found in a large number ofgeneral publications but these are described in detail, for example, inJ. A. Dean (compiler), Lange's Handbook of Chemistry, 12th ed.,McGraw-Hill (1979), and Kagakuno Ryoiki (Chemistry Region), specialnumber, No. 122, pp. 96–103, Nankodo (1979). In the present invention,each substituent is limited or described by using the Hammett'ssubstituent constant σp but this does not mean that the substituent islimited only to those having a known value which can be found in theabove-described publications. Needless to say, the substituent includessubstituents of which σp value is not known in publications but whenmeasured based on the Hammett's rule, falls within the range specified.Furthermore, although formula (1a) of the present invention includesthose which are not a benzene derivative, the σp value is used as ameasure for showing the electron effect of the substituent irrespectiveof the substitution site. In the present invention, the σp value is usedin such a meaning.

Examples of the electron-withdrawing group having a Hammett'ssubstituent constant σp value of 0.60 or more include a cyano group, anitro group, an alkylsulfonyl group (e.g., methylsulfonyl) and anarylsulfonyl group (e.g., phenylsulfonyl).

Examples of the electron-withdrawing group having a Hammett's σp valueof 0.45 or more include, in addition to those described above, an acylgroup (e.g., acetyl), an alkoxycarbonyl group (e.g.,dodecyloxycarbonyl), an aryloxycarbonyl group (e.g.,m-chlorophenoxycarbonyl), an alkylsulfinyl group (e.g.,n-propylsulfinyl), an arylsulfinyl group (e.g., phenylsulfinyl), asulfamoyl group (e.g., N-ethylsulfamoyl, N,N-dimethylsulfamoyl) and ahalogenated alkyl group (e.g., trifluoromethyl).

Examples of the electron-withdrawing group having a Hammett'ssubstituent constant σp value of 0.30 or more include, in addition tothose described above, an acyloxy group (e.g., acetoxy), a carbamoylgroup (e.g., N-ethylcarbamoyl, N,N-dibutylcarbamoyl), a halogenatedalkoxy group (e.g., trifluoromethyloxy), a halogenated aryloxy group(e.g., pentafluorophenyloxy), a sulfonyloxy group (e.g.,methylsulfonyloxy), a halogenated alkylthio group (e.g.,difluoromethylthio), an aryl group substituted by two or moreelectron-withdrawing groups having a σp value of 0.15 or more (e.g.,2,4-dinitrophenyl, pentachlorophenyl) and a heterocyclic ring (e.g.,2-benzoxazolyl, 2-benzothiazolyl, 1-phenyl-2-benzimidazolyl).

Specific examples of the electron-withdrawing group having a σp value of0.20 or more include, in addition to those described above, a halogenatom.

The preferred combination of substituents in the azo dye represented byformula (1) is described below. R⁵ and R⁶ each is preferably a hydrogenatom, an alkyl group, an aryl group, a heterocyclic group, a sulfonylgroup or an acyl group, more preferably a hydrogen atom, an aryl group,a heterocyclic group or a sulfonyl group, and most preferably a hydrogenatom, an aryl group or a heterocyclic group. However, R⁵ and R⁶ are nota hydrogen atom at the same time.

G is preferably a hydrogen atom, a halogen atom, an alkyl group, ahydroxyl group, an amino group or an acylamino group, more preferably ahydrogen atom, a halogen atom, an amino group or an acylamino group, andmost preferably a hydrogen atom, an amino group or an acylamino group.

A is preferably a pyrazole ring, an imidazole ring, an isothiazole ring,a thiadiazole ring or a benzothiazole ring, more preferably a pyrazolering or an isothiazole ring, and most preferably a pyrazole ring.

B¹ and B² each is ═CR¹— or —CR²═, and R¹ and R² each is preferably ahydrogen atom, an alkyl group, a halogen atom, a cyano group, acarbamoyl group, a carboxyl group, a hydroxyl group, an alkoxy group oran alkoxycarbonyl group, more preferably a hydrogen atom, an alkylgroup, a carboxyl group, a cyano group or a carbamoyl group.

As for the preferred combination of substituents in the compoundrepresented by formula (1), a compound where at least one of varioussubstituents is the preferred group is preferred, a compound where alarger number of various substituents are the preferred groups is morepreferred, and a compound where all substituents are the preferredgroups is most preferred.

Specific examples of the azo dye represented by formula (1) are shownbelow as Compounds a-1 to a-46, b-1 to b-8, c-1 to c-5, d-1 to d-5, e-1to e-5, f-1 and f-2, but the azo dye for use in the present invention isnot limited to these examples.

Dye R₁ R₂ R₃ a-1 

a-2 

a-3 

a-4 

a-5 

a-6 

a-7 

a-8 

a-9 

C₈H₁₇(t) a-10

Dye R₁ R₂ R₃ R₄ a-11

a-12

a-13

a-14

a-15

a-16

a-17

Dye R₁ R₂ R₃ R₄ a-18

a-19

—SO₂CH₃

a-20

—COCH₃ C₈H₁₇(t) C₈H₁₇(t) a-21

—SO₂CH₃

C₈H₁₇(t) a-22

H

a-23

H

a-24

H

a-25

a-26

a-27

a-28

a-29

a-30

C₈H₁₇(t) a-31

a-32

a-33

a-34

a-35

a-36

a-37

a-38

a-39

a-40

Dye R₁ R₂ R₃ R₄ R₅ R₆ R₇ R₈ a-41

CN

H CONH₂ SO₂CH₃

a-42

Br

COOEt H

C₈H₁₇(t) COCH₃ a-43

SO₂CH₃

CONH₂ H

a-44

CN

H H

SO₂CH₃ a-45

Br

H CONH₂

a-46

CN

CH₃ H

Dye R₁ R₂ R₃ R₄ R₅ R₆ b-1 CH₃ CH₃ CN H

b-2 CH₃ CH₃ CN H

b-3 CH₃ CH₃ CONH₂ H

b-4 CH₃ CH₃ H H

b-5 CH₃ H CN H

b-6 CH₃ CH₃ H

b-7 CH₃ CH₃ H

b-8 CH₃ H H SO₂CH₃

Dye R₁ R₂ R₃ R₄ c-1 —SCH₃ CH₃ CN H c-2

H CONH₂ H c-3

CH₃ H

c-4 —CH₃ CH₃ H

c-5

H H

Dye R₅ R₆ c-1 C₈H₁₇(t)

c-2

c-3

c-4

c-5

C₈H₁₇(t)

Dye R₁ R₂ R₃ R₄ R₅ R₆ d-1 Me CH₃ CN H

d-2 Me CH₃ CN H

d-3 Me H H

d-4 Ph CH₃ CONH₂ H

d-5 Ph CH₃ H

Dye R₁ R₂ R₃ R₄ R₅ R₆ e-1 5-Cl CH₃ CONH₂ H C₈H₁₇(t) C₈H₁₇(t) e-25,6-diCl H H

e-3 5,6-diCl CH₃ H

COCH₃ e-4 5-CH₃ H CN H

e-5 5-NO₂ CH₃ H SO₂CH₃

f-1 f-2

The inkjet recording magenta ink of the present invention has a mainabsorption region of 500 to 580 nm and is preferably obtained bydissolving or dispersing at least one of the above-described azo dyes inan aqueous medium. In this case, the azo dye is preferably contained inan amount of 0.2 to 20 mass %, more preferably from 0.5 to 15 mass %,and the solubility in water at 20° C. (or dispersion degree in a stablestate) is preferably 5 mass % or more, more preferably 10 mass % ormore.

The dye of formula (1) for use in the present invention is substantiallywater-soluble or water-dispersible, more specifically, the solubility ofthe coloring material in water at 20° C. is preferably 2 mass % or more,more preferably 5 mass % or more.

In preparing a set comprising two or more inks sharing the mainabsorption region, generally, one ink is produced as a light-type thinink and another is produced as a thick ink, but in the presentinvention, the inks may be produced as different type inks in this wayor may be produced as inks having almost the same concentration.

In the case of two or more inks sharing the main absorption region areused in combination as a set, the dye contained in each ink may be asingle dye or a mixture of dyes, but in either case, at least one inkpreferably contains at least one dye represented by formula (1) in theform of being dissolved or dispersed in an aqueous medium and theconcentration of the dye is from 0.2 to 20 mass %, more preferably from0.5 to 15 mass %.

On the other hand, the coloring material combined with the dyerepresented by formula (1) may be either a dye or a pigment and may bein the form of being dissolved in an aqueous medium or in the form thata pigment insoluble in the aqueous medium is present in the dispersedstate. In the case of a pigment, the solubility (at 25° C.) in water is0.1 g/100 g or less in many cases. As for the ink where the component isdispersed, examples of the component include an emulsion dispersion, apolymer dye, a dye supported on or dispersed in a polymer, and apigment. Among these, a pigment is preferred.

Also, the dye ink may contain a water-insoluble pigment in the dispersedstate or the pigment ink may contain a water-soluble dye.

When a dye represented by formula (1) and a different dye or a pigmentare present in combination in one ink, the total concentration thereofis from 0.2 to 20 mass %, preferably from 0.5 to 15 mass %.

The magenta dye having an azo group for use in the present invention hasan oxidation potential, in an aqueous medium for ink, nobler than 0.7 Vvs SCE, preferably nobler than 0.8 V vs SCE, more preferably nobler than1.0 V vs SCE. The potential can be elevated by selecting the preferredstructural features described above, more specifically, by selecting adye structure of a type having a chromophore represented by(heterocyclic ring A)-N═N-(heterocyclic ring B), selecting an azo dye inwhich an aromatic nitrogen-containing 6-membered heterocyclic ring isbonded as a coupling component directly to at least one side of the azogroup, and selecting an azo dye having an aromatic ring amino group- orheterocyclic amino group-containing structure as an auxochrome, andfurthermore by removing a hydrogen of the azo dye. In particular, thedye of formula (1) expresses a noble potential. This is specificallydescribed in Japanese Patent Application No. 2001-254878.

The oxidation potential value (Eox) can be easily measured by oneskilled in the art and the method therefor is described, for example, inP. Delahay, New Instrumental Methods in Electrochemistry, IntersciencePublishers (1954), A. J. Bard et al., Electrochemical Methods, JohnWiley & Sons (1980), and Akira Fujishima et al., Denkikagaku Sokutei Ho(Electrochemical Measuring Method), Gihodo Shuppan Sha (1984).

More specifically, the oxidation potential can be measured by variousmeasuring methods such as direct current polarography which is a methodof measuring the oxidation potential in an aqueous solution orwater-mixed solvent system having dissolved therein the dye based on SCE(standard saturated calomel electrode) as the reference electrode and inwhich a graphite electrode and a platinum electrode are used as theworking electrode and the counter electrode, respectively; polarographyin which a dropping mercury electrode is used; cyclic voltammetry method(CV); rotating ring-disk electrode method; and comb electrode method.The oxidation potential is measured as follows. A test sample isdissolved to a concentration of 1×10⁻⁴ to 1×10⁻⁶ mol·dm⁻³ in a solventsuch as dimethylformamide or acetonitrile containing a supportingelectrolyte such as sodium perchlorate or tetrapropylammoniumperchlorate and the oxidation potential is measured as a value to SCE(standard saturated calomel electrode) by using the above-describedmethod. The supporting electrolyte and solvent used can be appropriatelyselected according to the oxidation potential or solubility of the testsample. The supporting electrolyte and solvent which can be used aredescribed in Akira Fujishima et al., Denkikagaku Sokutei Ho(Electrochemical Measuring Method), pp. 101–118, Gihodo Shuppan Sha(1984).

The oxidation potential value sometimes deviates on the order of severaltens of millivolt due to the effect of, for example, liquid junctionpotential or liquid resistance of sample solution, but thereproducibility of measured potential value can be guaranteed by thecalibration using a standard sample (for example, hydroquinone) and thesame measured value can be obtained by any of those potential measuringmethods.

<Coloring Materials Sharing Main Absorption Region of 580 to 680 nm>

The coloring material of the cyan ink which is combined with the magentaink for forming a full color image is described below. The coloringmaterials contained in the inkjet recording cyan ink for use in thepresent invention are coloring materials sharing the main absorptionregion of 580 to 680 nm. At least one of the constituent coloringmaterials is preferably a phthalocyanine dye represented by formula (I).

The phthalocyanine dye is a dye having fastness but this dye is known tobe inferior in the fastness to ozone gas when used as a dye for inkjetrecording. In the phthalocyanine dye represented by formula (I), thisdefect is overcome by its chemical structure.

In the phthalocyanine dye represented by formula (I), anelectron-withdrawing group is introduced into the phthalocyanineskeleton so as to reduce the reactivity with ozone which is anelectrophilic agent. The oxidation potential of this dye is nobler than0.7 V (vs SCE) in many cases. A nobler oxidation potential is morepreferred and the oxidation potential is more preferably nobler than 1.0V (vs SCE) and most preferably nobler than 1.2 V (vs SCE).

The oxidation potential (sometimes also referred to as “Eox”) valueindicates the transferability of an electron from the sample to theelectrode and as the value is larger (the oxidation potential isnobler), the electron is less transferable from the sample to theelectrode, in other words, the oxidation less occurs. As for therelationship with the structure of compound, the oxidation potentialbecomes nobler when an electron-withdrawing group is introduced, andbecomes baser when an electron-donating group is introduced. In thepresent invention, the oxidation potential is preferably rendered noblerby introducing an electron-withdrawing group into the phthalocyanineskeleton so as to reduce the reactivity with ozone which is anelectrophilic agent. When the Hammett's substituent constant σp value asa measure for the electron-withdrawing property or electron-donatingproperty of substituent is used, the oxidation potential can be renderednobler by introducing a substituent having a large op value, such assulfinyl group, sulfonyl group and sulfamoyl group.

Also for the purpose of such potential control, the phthalocyanine dyerepresented by formula (I) is preferably used.

The oxidation potential of the phthalocyanine dye is measured bycommonly employed methods described above.

In formula (I), X₁, X₂, X₃ and X₄ each independently represents —SO-Z,—SO₂-Z, —SO₂NR₁R₂, a sulfo group, —CONR₁R₂ or —CO₂R₁. Among thesesubstituents, preferred are —SO-Z, —SO₂-Z, —SO₂NR₁R₂ and —CONR₁R₂, morepreferred are —SO₂-Z and —SO₂NR₁R₂, and most preferred is —SO₂-Z. In thecase where a₁ to a₄ showing the number of substituents each represents anumber of 2 or more, a plurality of substituents X₁, X₂, X₃ or X₄ may bethe same or different and each independently represents any one of theabove-described groups. X₁, X₂, X₃ and X₄ may be completely the samesubstituents, may be substituents of the same kind but partiallydifferent as in the case, for example, where X₁, X₂, X₃ and X₄ all are—SO₂-Z and Zs are different from each other, or may contain substituentsdifferent from each other, for example, —SO₂-Z and —SO₂NR₁R₂.

Each Z independently represents a substituted or unsubstituted alkylgroup, a substituted or unsubstituted cycloalkyl group, a substituted orunsubstituted alkenyl group, a substituted or unsubstituted aralkylgroup, a substituted or unsubstituted aryl group, or a substituted orunsubstituted heterocyclic group, preferably a substituted orunsubstituted alkyl group, a substituted or unsubstituted aryl group ora substituted or unsubstituted heterocyclic group, and most preferably asubstituted alkyl group, a substituted aryl group or a substitutedheterocyclic group.

R₁ and R₂ each independently represents a hydrogen atom, a substitutedor unsubstituted alkyl group, a substituted or unsubstituted cycloalkylgroup, a substituted or unsubstituted alkenyl group, a substituted orunsubstituted aralkyl group, a substituted or unsubstituted aryl group,or a substituted or unsubstituted heterocyclic group, preferably ahydrogen atom, a substituted or unsubstituted alkyl group, a substitutedor unsubstituted aryl group, or a substituted or unsubstitutedheterocyclic group, more preferably a hydrogen atom, a substituted alkylgroup, a substituted aryl group or a substituted heterocyclic group.However, it is not preferred that R₁ and R₂ both are a hydrogen atom.

The substituted or unsubstituted alkyl group represented by R₁, R₂ and Zis preferably an alkyl group having from 1 to 30 carbon atoms, morepreferably a branched alkyl group because the solubility of dye and thestability of ink are improved, still more preferably an alkyl grouphaving an asymmetric carbon (use in the racemic form). Examples of thesubstituent include those described later as the substituent when Z, R₁,R₂, Y₁, Y₂, Y₃ and Y₄ can further have a substituent. In particular, ahydroxyl group, an ether group, an ester group, a cyano group, an amidogroup and a sulfonamido group are preferred because the aggregatingproperty and fastness of dye are enhanced. Other than these, the alkylgroup may be substituted by a halogen atom or an ionic hydrophilicgroup. Incidentally, the number of carbon atoms in the alkyl group doesnot contain carbon atoms of substituents and this applies to othergroups.

The substituted or unsubstituted cycloalkyl group represented by R₁, R₂and Z is preferably a cycloalkyl group having from 5 to 30 carbon atoms,more preferably a cycloalkyl group having an asymmetric carbon (use inthe racemic form) because the solubility of dye and the stability of inkare improved. Examples of the substituent include those described lateras the substituent when Z, R₁, R₂, Y₁, Y₂, Y₃ and Y₄ can further have asubstituent. In particular, a hydroxyl group, an ether group, an estergroup, a cyano group, an amido group and a sulfonamido group arepreferred because the aggregating property and fastness of dye areenhanced. Other than these, the cycloalkyl group may be substituted by ahalogen atom or an ionic hydrophilic group.

The substituted or unsubstituted alkenyl group represented by R₁, R₂ andZ is preferably an alkenyl group having from 2 to 30 carbon atoms, morepreferably a branched alkenyl group because the solubility of dye andthe stability of ink are improved, still more preferably an alkenylgroup having an asymmetric carbon (use in the racemic form). Examples ofthe substituent include those described later as the substituent when Z,R₁, R₂, Y₁, Y₂, Y₃ and Y₄ can further have a substituent. In particular,a hydroxyl group, an ether group, an ester group, a cyano group, anamido group and a sulfonamido group are preferred because theaggregating property and fastness of dye are enhanced. Other than these,the alkenyl group may be substituted by a halogen atom or an ionichydrophilic group.

The substituted or unsubstituted aralkyl group represented by R₁, R₂ andZ is preferably an aralkyl group having from 7 to 30 carbon atoms, morepreferably a branched aralkyl group because the solubility of dye andthe stability of ink are improved, still more preferably an aralkylgroup having an asymmetric carbon (use in the racemic form). Examples ofthe substituent include those described later as the substituent when Z,R₁, R₂, Y₁, Y₂, Y₃ and Y₄ can further have a substituent. In particular,a hydroxyl group, an ether group, an ester group, a cyano group, anamido group and a sulfonamido group are preferred because theaggregating property and fastness of dye are enhanced. Other than these,the aralkyl group may be substituted by a halogen atom or an ionichydrophilic group.

The substituted or unsubstituted aryl group represented by R₁, R₂ and Zis preferably an aryl group having from 6 to 30 carbon atoms. Examplesof the substituent include those described later as the substituent whenZ, R₁, R₂, Y₁, Y₂, Y₃ and Y₄ can further have a substituent. Inparticular, an electron-withdrawing group is preferred because the dyecan have a noble oxidation potential and can be improved in thefastness. Examples of the electron-withdrawing group include thosehaving a positive Hammett's substituent constant σp value. Among these,preferred are a halogen atom, a heterocyclic group, a cyano group, acarboxyl group, an acylamino group, a sulfonamido group, a sulfamoylgroup, a carbamoyl group, a sulfonyl group, an imido group, an acylgroup, a sulfo group and a quaternary ammonium group, more preferred area cyano group, a carboxyl group, a sulfamoyl group, a carbamoyl group, asulfonyl group, an imido group, an acyl group, a sulfo group and aquaternary ammonium group.

The heterocyclic group represented by R₁, R₂ and Z is preferably a 5- or6-membered ring and the ring may be further condensed. Also, theheterocyclic group may be an aromatic heterocyclic group or anon-aromatic heterocyclic group. Examples of the heterocyclic grouprepresented by R₁, R₂ and Z are shown below in the form of aheterocyclic ring by omitting the substitution site. The substitutionsite is not limited and, for example, in the case of pyridine, the2-position, 3-position and 4-position can be substituted. Examplesinclude pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline,isoquinoline, quinazoline, cinnoline, phthalazine, quinoxaline, pyrrole,indole, furan, benzofuran, thiophene, benzothiophene, pyrazole,imidazole, benzimidazole, triazole, oxazole, benzoxazole, thiazole,benzothiazole, isothiazole, benzisothiazole, thiadiazole, isoxazole,benzisoxazole, pyrrolidine, piperidine, piperazine, imidazolidine andthiazoline. In particular, an aromatic heterocyclic group is preferred.Preferred examples thereof include, shown in the same manner as above,pyridine, pyrazine, pyrimidine, pyridazine, triazine, pyrazole,imidazole, benzimidazole, triazole, thiazole, benzothiazole,isothiazole, benzisothiazole and thiadiazole. These groups each may havea substituent and examples of the substituent include those describedlater as the substituent when Z, R₁, R₂, Y₁, Y₂, Y₃ and Y₄ can furtherhave a substituent. Preferred substituents are the same as thesubstituents of the above-described aryl group and more preferredsubstituents are the same as the more preferred substituents of theabove-described aryl group.

Y₁, Y₂, Y₃ and Y₄ each independently represents a hydrogen atom, ahalogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, anaralkyl group, an aryl group, a heterocyclic group, a cyano group, ahydroxyl group, a nitro group, an amino group, an alkylamino group, analkoxy group, an aryloxy group, an acylamino group, an arylamino group,a ureido group, a sulfamoylamino group, an alkylthio group, an arylthiogroup, an alkoxycarbonylamino group, a sulfonamido group, a carbamoylgroup, a sulfamoyl group, a sulfonyl group, an alkoxycarbonyl group, aheterocyclic oxy group, an azo group, an acyloxy group, a carbamoyloxygroup, a silyloxy group, an aryloxycarbonyl group, anaryloxycarbonylamino group, an imido group, a heterocyclic thio group, aphosphoryl group, an acyl group, a carboxyl group or a sulfo group.These groups each may further have a substituent.

Y₁, Y₂, Y₃ and Y₄ each is preferably a hydrogen atom, a halogen atom, analkyl group, an aryl group, a cyano group, an alkoxy group, an amidogroup, a ureido group, a sulfonamido group, a carbamoyl group, asulfamoyl group, an alkoxycarbonyl group, a carboxyl group or a sulfogroup, more preferably a hydrogen atom, a halogen atom, a cyano group, acarboxyl group or a sulfo group, and most preferably a hydrogen atom.

When Z, R₁, R₂, Y₁, Y₂, Y₃ and Y₄ each is a group which can further havea substituent, the group may further have a substituent described below.

Examples of the substituent include a linear or branched alkyl grouphaving from 1 to 12 carbon atoms, a linear or branched aralkyl grouphaving from 7 to 18 carbon atoms, a linear or branched alkenyl grouphaving from 2 to 12 carbon atoms, a linear or branched alkynyl grouphaving from 2 to 12 carbon atoms, a linear or branched cycloalkyl grouphaving from 3 to 12 carbon atoms, a linear or branched cycloalkenylgroup having from 3 to 12 carbon atoms (these groups each is preferablya group having a branched chain because the solubility of dye and thestability of ink are improved, more preferably a group having anasymmetric carbon; specific examples of the groups include methyl,ethyl, propyl, isopropyl, sec-butyl, tert-butyl, 2-ethylhexyl,2-methylsulfonylethyl, 3-phenoxypropyl, trifluoromethyl andcyclopentyl), a halogen atom (e.g., chlorine, bromine), an aryl group(e.g., phenyl, 4-tert-butylphenyl, 2,4-di-tert-amylphenyl), aheterocyclic group (e.g., imidazolyl, pyrazolyl, triazolyl, 2-furyl,2-thienyl, 2-pyrimidinyl, 2-benzothiazolyl), a cyano group, a hydroxylgroup, a nitro group, a carboxy group, an amino group, an alkyloxy group(e.g., methoxy, ethoxy, 2-methoxyethoxy, 2-methanesulfonylethoxy), anaryloxy group (e.g., phenoxy, 2-methylphenoxy, 4-tert-butylphenoxy,3-nitrophenoxy, 3-tert-butyloxycarbamoylphenoxy, 3-methoxycarbamoyl), anacylamino group (e.g., acetamido, benzamido,4-(3-tert-butyl-4-hydroxyphenoxy)butanamido), an alkylamino group (e.g.,methylamino, butylamino, diethylamino, methylbutylamino), an anilinogroup (e.g., phenylamino, 2-chloroanilino), a ureido group (e.g.,phenylureido, methylureido, N,N-dibutylureido), a sulfamoylamino group(e.g., N,N-dipropylsulfamoylamino), an alkylthio group (e.g.,methylthio, octylthio, 2-phenoxyethylthio), an arylthio group (e.g.,phenylthio, 2-butoxy-5-tert-octylphenylthio, 2-carboxyphenylthio), analkyloxycarbonylamino group (e.g., methoxycarbonylamino), a sulfonamidogroup (e.g., methanesulfonamido, benzenesulfonamido,p-toluenesulfonamido), a carbamoyl group (e.g., N-ethylcarbamoyl,N,N-dibutylcarbamoyl), a sulfamoyl group (e.g., N-ethylsulfamoyl,N,N-dipropylsulfamoyl, N-phenylsulfamoyl), a sulfonyl group (e.g.,methanesulfonyl, octanesulfonyl, benzenesulfonyl, toluenesulfonyl), analkyloxycarbonyl group (e.g., methoxycarbonyl, butyloxycarbonyl), aheterocyclic oxy group (e.g., 1-phenyltetrazol-5-oxy,2-tetrahydropyranyloxy), an azo group (e.g., phenylazo,4-methoxyphenylazo, 4-pivaloylaminophenylazo,2-hydroxy-4-propanoylphenylazo), an acyloxy group (e.g., acetoxy), acarbamoyloxy group (e.g., N-methylcarbamoyloxy, N-phenylcarbamoyloxy), asilyloxy group (e.g., trimethylsilyloxy, dibutylmethylsilyloxy), anaryloxycarbonylamino group (e.g., phenoxycarbonylamino), an imido group(e.g., N-succinimido, N-phthalimido), a heterocyclic thio group (e.g.,2-benzothiazolylthio, 2,4-di-phenoxy-1,3,5-triazole-6-thio,2-pyridylthio), a sulfinyl group (e.g., 3-phenoxypropylsulfinyl), aphosphonyl group (e.g., phenoxyphosphonyl, octyloxyphosphonyl,phenylphosphonyl), an aryloxycarbonyl group (e.g., phenoxycarbonyl), anacyl group (e.g., acetyl, 3-phenylpropanoyl, benzoyl), and an ionichydrophilic group (e.g., carboxyl, sulfo, phosphono, quaternaryammonium).

In the case where the phthalocyanine dye represented by formula (I) iswater-soluble, the dye preferably contains an ionic hydrophilic group.Examples of the ionic hydrophilic group include a sulfo group, acarboxyl group, a phosphono group and a quaternary ammonium group. Amongthese ionic hydrophilic groups, preferred are a carboxyl group, aphosphono group and a sulfo group, more preferred are a carboxyl groupand a sulfo group. The carboxyl group, the phosphono group and the sulfogroup each may be in a salt state and examples of the counter ion forforming the salt include ammonium ion, alkali metal ions (e.g., lithiumion, sodium ion, potassium ion) and organic cations (e.g.,tetramethylammonium ion, tetramethylguanidium ion,tetramethylphosphonium). Among these counter ions, alkali metal saltsare preferred and a lithium salt is more preferred because thesolubility of dye and the stability of ink are enhanced.

As for the number of ionic hydrophilic groups, the phthalocyanine dyepreferably contains at least two ionic hydrophilic groups, morepreferably at least two sulfo groups and/or carboxyl groups, within onemolecule.

a₁ to a₄ and b₁ to b₄ represent the number of substituents X₁ to X₄ andY₁ to Y₄, respectively. a₁ to a₄ each independently represents aninteger of 0 to 4 but all are not 0 at the same time. b₁ to b₄ eachindependently represents an integer of 0 to 4. When a₁, a₂, a₃, a₄, b₁,b₂, b₃ or b₄ represents an integer of 2 or more, a plurality of X₁s,X₂s, X₃s, X₄s, Y₁s, Y₂s, Y₃s or Y₄s are present and these may be thesame or different.

a₁ and b₁ satisfy the relationship of a₁+b₁=4. In particular, acombination that a₁ represents 1 or 2 and b₁ represents 3 or 2 ispreferred, and a combination that a₁ represents 1 and b₁ represents 3 ismost preferred.

The same relationship as that between a₁ and b₁ is present in each ofthe pairs a₂ and b₂, a₃ and b₃, and a₄ and b₄, and the preferredcombination is also the same.

M represents a hydrogen atom, a metal element or an oxide, hydroxide orhalide thereof.

M is preferably a hydrogen atom, a metal element such as Li, Na, K, Mg,Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt,Cu, Ag, Au, Zn, Cd, Hg, Al, Ga, In, Si, Ge, Sn, Pb, Sb and Bi, an oxidesuch as VO and GeO, a hydroxide such as Si(OH)₂, Cr(OH)₂ and Sn(OH)₂, ora halide such as AlCl, SiCl₂, VCl, VCl₂, VOCl, FeCl, GaCl and ZrCl, morepreferably Cu, Ni, Zn or Al, and most preferably Cu.

Also, Pc (phthalocyanine ring) may form a dimer (for example,Pc-M-L-M-Pc) or a trimer through L (divalent linking group). At thistime, Ms may be the same or different.

The divalent linking group represented by L is preferably an oxy group—O—, a thio group —S—, a carbonyl group —CO—, a sulfonyl group —SO₂—, animino group —NH—, a methylene group —CH₂— or a group formed by combiningtwo or more of these groups.

As for the preferred combination of substituents in the compoundrepresented by formula (I), a compound where at least one of varioussubstituents is the preferred group is preferred, a compound where alarger number of various substituents are the preferred groups is morepreferred, and a compound where all substituents are the preferredgroups is most preferred.

Among the phthalocyanine dyes represented by formula (I), aphthalocyanine dye having a structure represented by formula (II) ispreferred. The phthalocyanine dye represented by formula (II) of thepresent invention is described in detail below.

In formula (II), X₁₁ to X₁₄ and Y₁₁ to Y₁₈ have the same meanings as X₁to X₄ and Y₁ to Y₄ in formula (I), respectively, and preferred examplesare also the same. M has the same meaning as M in formula (I) andpreferred examples are also the same.

In formula (II), a₁₁ to a₁₄ each independently represents an integer of1 or 2 and preferably satisfy 4≦a₁₁+a₁₂+a₁₃+a₁₄≦6, and a₁₁=a₁₂=a₁₃=a₁₄=1is more preferred.

X₁₁, X₁₂, X₁₃ and X₁₄ may be completely the same substituents, may besubstituents of the same kind but partially different as in the case,for example, where X₁₁, X₁₂, X₁₃ and X₁₄ all are —SO₂-Z and Zs aredifferent from each other, or may contain substituents different fromeach other, for example, —SO₂-Z and —SO₂NR₁R₂.

In the phthalocyanine dye represented by formula (II), the followingcombinations of substituents are particularly preferred.

X₁₁ to X₁₄ each independently represents preferably —SO-Z, —SO₂-Z,—SO₂NR₁R₂ or —CONR₁R₂, more preferably —SO₂-Z or —SO₂NR₁R₂, and mostpreferably —SO₂-Z.

Each Z independently represents preferably a substituted orunsubstituted alkyl group, a substituted or unsubstituted aryl group ora substituted or unsubstituted heterocyclic group, and most preferably asubstituted alkyl group, a substituted aryl group or a substitutedheterocyclic group. In particular, the case where an asymmetric carbonis present in the substituent (use in the racemic form) is preferredbecause the solubility of dye and the stability of ink are enhanced.Also, the case where a hydroxyl group, an ether group, an ester group, acyano group, an amido group or a sulfonamido group is present in thesubstituent is preferred because the aggregating property and fastnessare improved.

R₁ and R₂ each independently represents preferably a hydrogen atom, asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedaryl group or a substituted or unsubstituted heterocyclic group, morepreferably a hydrogen atom, a substituted alkyl group, a substitutedaryl group or a substituted heterocyclic group. However, it is notpreferred that R₁ and R₂ both are a hydrogen atom. In particular, thecase where an asymmetric carbon is present in the substituent (use inthe racemic form) is preferred because the solubility of dye and thestability of ink are enhanced. Also, the case where a hydroxyl group, anether group, an ester group, a cyano group, an amido group or asulfonamido group is present in the substituent is preferred because theaggregating property and fastness are improved.

Y₁₁ to Y₁₈ each independently represents preferably a hydrogen atom, ahalogen atom, an alkyl group, an aryl group, a cyano group, an alkoxygroup, an amido group, a ureido group, a sulfonamido group, a carbamoylgroup, a sulfamoyl group, an alkoxycarbonyl group, a carboxyl group or asulfo group, more preferably a hydrogen atom, a halogen atom, a cyanogroup, a carboxyl group or a sulfo group, and most preferably a hydrogenatom.

a₁₁ to a₁₄ each independently represents preferably 1 or 2 and it ismore preferred that all are 1.

M represents a hydrogen atom, a metal element or an oxide, hydroxide orhalide thereof, preferably Cu, Ni, Zn or Al, and most preferably Cu.

In the case where the phthalocyanine dye represented by formula (II) iswater-soluble, the dye preferably contains an ionic hydrophilic group.Examples of the ionic hydrophilic group include a sulfo group, acarboxyl group, a phosphono group and a quaternary ammonium group. Amongthese ionic hydrophilic groups, preferred are a carboxyl group, aphosphono group and a sulfo group, more preferred are a carboxyl groupand a sulfo group. The carboxyl group, the phosphono group and the sulfogroup each may be in a salt state and examples of the counter ion forforming the salt include ammonium ion, alkali metal ions (e.g., lithiumion, sodium ion, potassium ion) and organic cations (e.g.,tetramethylammonium ion, tetramethylguanidium ion,tetramethylphosphonium). Among these counter ions, alkali metal saltsare preferred and a lithium salt is more preferred because thesolubility of dye and the stability of ink are enhanced.

As for the number of ionic hydrophilic groups, the phthalocyanine dyepreferably contains at least two ionic hydrophilic groups, morepreferably at least two sulfo groups and/or carboxyl groups, within onemolecule.

As for the preferred combination of substituents in the compoundrepresented by formula (II), a compound where at least one of varioussubstituents is the preferred group is preferred, a compound where alarger number of various substituents are the preferred groups is morepreferred, and a compound where all substituents are the preferredgroups is most preferred.

As for the chemical structure of the phthalocyanine dye of the presentinvention, at least one electron-withdrawing group such as sulfinylgroup, sulfonyl group and sulfamoyl group is preferably introduced intorespective four benzene rings of phthalocyanine such that the total ofσp values of the substituents in the entire phthalocyanine skeletonbecomes 1.6 or more.

The Hammett's substituent constant σp value is briefly described here.The Hammett's rule is an empirical rule advocated by L. P. Hammett in1935 so as to quantitatively discuss the effect of substituent on thereaction or equilibrium of benzene derivatives and its propriety iswidely admitted at present. The substituent constant determined by theHammett's rule includes a σp value and a σm value and these values canbe found in a large number of general publications but these aredescribed in detail, for example, in J. A. Dean (compiler), Lange'sHandbook of Chemistry, 12th ed., McGraw-Hill (1979), and Kagakuno Ryoiki(Chemistry Region), special number, No. 122, pp. 96–103, Nankodo (1979).

Inevitably in view of the synthesis method, the phthalocyaninederivative represented by formula (I) is generally a mixture ofanalogues differing in the site where the substituents Xn (n=1 to 4) andYm (m=1 to 4) are introduced and in the number of the substituentsintroduced. Accordingly, these analogue mixtures are statisticallyaveraged and represented by a formula in many cases. In the presentinvention, it has been found that when these analogue mixtures areclassified into the following three types, a specific mixture isparticularly preferred. The phthalocyanine-base dye analogue mixturesrepresented by formulae (I) and (II) are defined by classifying theseinto the following three types based on the substitution site.

(1) β-Position Substitution Type:

A phthalocyanine dye having specific substituents at the 2- and/or3-position, the 6- and/or 7-position, the 10- and/or 11-position, andthe 14- and/or 15-position.

(2) α-Position Substitution Type:

A phthalocyanine dye having specific substituents at the 1- and/or4-position, the 5- and/or 8-position, the 9- and/or 12-position, and the13- and/or 16-position.

(3) α,β-Position Mixed Substitution Type:

A phthalocyanine dye having specific substitutions at the 1- to16-positions without any regularity.

In the present invention, phthalocyanine dye derivatives differing inthe structure (particularly in the substitution site) are described byusing these β-position substitution type, α-position substitution typeand α,β-position mixed substitution type.

The phthalocyanine derivative for use in the present invention can besynthesized by combining the methods described or cited, for example, inShirai and Kobayashi, Phthalocyanine—Kagaku toKino—(Phthalocyanine—Chemistry and Function—), pp. 1–62, IPC, and C. C.Leznoff and A. B. P. Lever, Phthalocyanines—Properties and Applications,pp. 1–54, VCH, or methods analogous thereto.

The phthalocyanine compound represented by formula (I) of the presentinvention can be synthesized, for example, through sulfonation, sulfonylchloridation or amidation reaction of an unsubstituted phthalocyaninecompound as described in International Publications 00/17275, 00/08103,00/08101 and 98/41853 and JP-A-10-36471. In this case, sulfonation maytake place at any site of the phthalocyanine nucleus and the number ofsites sulfonated is difficult to control. Accordingly, when a sulfogroup is introduced under such reaction conditions, the positions andnumber of sulfo groups introduced into the product cannot be specifiedand a mixture of those differing in the number of substituents or in thesubstitution site inevitably results. If the compound of the presentinvention is synthesized starting from such a product, the compound ofthe present invention is obtained as an α,β-position mixed substitutiontype mixture containing several kinds of compounds differing in thenumber of substituents or in the substitution site because the number ofsulfamoyl groups substituted on the heterocyclic ring or theirsubstitution sites cannot be specified.

As described above, for example, when many electron-withdrawing groupssuch as sulfamoyl group are introduced into the phthalocyanine nucleus,the oxidation potential becomes nobler and the ozone resistance isincreased. However, according to the above-described synthesis method, aphthalocyanine dye where the number of electron-withdrawing groupsintroduced is small, namely, the oxidation potential is baser, isinevitably mingled. Therefore, in order to improve the ozone resistance,it is preferred to use a synthesis method where the production of acompound having a baser oxidation potential is suppressed.

The phthalocyanine compound represented by formula (II) for use in thepresent invention can be synthesized, for example, by reacting aphthalonitrile derivative (Compound P) shown below and/or adiiminoisoindoline derivative (Compound Q) shown below with a metalderivative represented by formula (III) or can be derived from atetrasulfophthalocyanine compound obtained by reacting a4-sulfophthalonitrile derivative (Compound R) shown below with a metalderivative represented by formula (III).

In the formulae above, X_(p) corresponds to X₁₁, X₁₂, X₁₃ or X₁₄ informula (II) and Y_(q) and Y_(q′) each corresponds to Y₁₁, Y₁₂, Y₁₃,Y₁₄, Y₁₅, Y₁₆, Y₁₇ or Y₁₈ in formula (II). In Compound R, M′ representscation.

Examples of the cation represented by M′ include alkali metal ions suchas Li, Na and K, and organic cations such as triethylammonium ion andpyridinium ion.M-(Y)_(d)  Formula (III):wherein M has the same meaning as M in formulae (I) and (II), Yrepresents a monovalent or divalent ligand such as halogen atom, acetateanion, acetylacetonate and oxygen, and d represents an integer of 1 to4.

That is, according to this synthesis method, a specific number ofdesired substituents can be introduced. Particularly, in the case ofintroducing a large number of electron-withdrawing groups so as torender the oxidation potential nobler as in the present invention, thissynthesis method is very excellent as compared with the above-describedmethod for synthesizing the phthalocyanine compound of formula (I).

The thus-obtained phthalocyanine compound represented by formulae (II)is usually a mixture of compounds represented by the following formulae(a)-1 to (a)-4 which are isomers with respect to the substitution siteof each X_(p), namely, a β-position substitution type.

In the synthesis method above, when all X_(p)s are the same, aβ-position substitution type phthalocyanine dye where X₁₁, X₁₂, X₁₃ andX₁₄ are completely the same substituents can be obtained. On the otherhand, when X_(p)s are different, a dye having substituents of the samekind but partially different from each other or a dye havingsubstituents different from each other can be synthesized. Among thedyes of formula (II), these dyes having electron-withdrawingsubstituents different from each other are preferred because thesolubility and aggregating property of dye and the aging stability ofink can be controlled.

In the present invention, it has been found very important for theimprovement of fastness that in any substitution type, the oxidationpotential is nobler than 1.0 V (vs SCE). The great effect thereof cannotbe expected at all from the above-described known techniques.Furthermore, although the reason is not particularly known, there is atendency that the β-position substitution type is apparently moreexcellent in the color hue, light fastness, ozone gas resistance and thelike than the α,β-position mixed substitution type.

Specific examples (Compounds I-1 to I-12 and 101 to 190) of thephthalocyanine dyes represented by formulae (I) and (II) are set forthbelow, but the phthalocyanine dye for use in the present invention isnot limited to the following examples.

In the following Tables, specific examples of each pair of (X₁, X₂),(Y₁₁, Y₁₂), (Y₁₃, Y₁₄), (Y₁₅, Y₁₆) and (Y₁₇, Y₁₈) are independently inan irregular order.

Compound No. M X₁ 101 Cu —SO₂—NH—CH₂—CH₂—SO₃Li 102 Cu

103 Cu

104 Cu

105 Ni

106 Cu —SO₂—NH—CH₂—CH₂—SO₂—NH—CH₂—COONa 107 Cu

108 Cu —SO₂—CH₂—CH₂—CH₂—SO₃Li 109 Cu —SO₂—CH₂—CH₂—CH₂—SO₃K 110 Cu—SO₂—(CH₂)₅—CO₂K 111 Cu

112 Cu

113 Cu

114 Cu

115 Cu

116 Cu

117 Cu

118 Cu

119 Cu

120 Cu

121 Cu

122 Cu

123 Cu —SO₂NH—C₈H₁₇(t) 124 Cu

125 Cu

126 Cu

127 Cu

128 Zn

129 Cu

130 Cu

131 Cu

132 Cu

133 Cu

134 Cu

135 Cu

136 Cu

137 Cu

138 Cu

139 Cu

140 Cu

141 Cu

142 Cu

143 Cu

144 Cu

145 Cu —SO₂CH₂CH₂OCH₂CH₂OCH₂CH₂SO₃Li Compound No. X₂ Y₁₁, Y₁₂ Y₁₃, Y₁₄Y₁₅, Y₁₆ Y₁₇, Y₁₈ 101 —H —H, —H —H, —H —H, —H —H, —H 102 —H —Cl, —H —Cl,—H —Cl, —H —Cl, —H 103 —H —H, —H —H, —H —H, —H —H, —H 104 —H —H, —H —H,—H —H, —H —H, —H 105 —H —Cl, —H —Cl, —H —Cl, —H —Cl, —H 106 —CN —H, —H—H, —H —H, —H —H, —H 107 —H —H, —H —H, —H —H, —H —H, —H 108 —H —H, —H—H, —H —H, —H —H, —H 109 —H —H, —H —H, —H —H, —H —H, —H 110 —H —H, —H—H, —H —H, —H —H, —H 111 —H —H, —H —H, —H —H, —H —H, —H 112 —SO₃Li —H,—H —H, —H —H, —H —H, —H 113 —H —H, —H —H, —H —H, —H —H, —H 114 —SO₃Li—H, —H —H, —H —H, —H —H, —H 115 —H —H, —H —H, —H —H, —H —H, —H 116 —H—H, —H —H, —H —H, —H —H, —H 117 —H —H, —H —H, —H —H, —H —H, —H 118 —H—H, —H —H, —H —H, —H —H, —H 119 —H —H, —H —H, —H —H, —H —H, —H 120 —H—H, —H —H, —H —H, —H —H, —H 121 —H —H, —H —H, —H —H, —H —H, —H 122 —H—H, —H —H, —H —H, —H —H, —H 123 —H —H, —H —H, —H —H, —H —H, —H 124 —H—H, —H —H, —H —H, —H —H, —H 125 —H —H, —H —H, —H —H, —H —H, —H 126 —H—H, —H —H, —H —H, —H —H, —H 127 —H —H, —H —H, —H —H, —H —H, —H 128 —CN—H, —H —H, —H —H, —H —H, —H 129 —H —Cl, —H —Cl, —H —Cl, —H —Cl, —H 130—H —H, —H —H, —H —H, —H —H, —H 131 —H —H, —H —H, —H —H, —H —H, —H 132 —H—H, —H —H, —H —H, —H —H, —H 133 —H —H, —H —H, —H —H, —H —H, —H 134 —H—H, —H —H, —H —H, —H —H, —H 135 —H —H, —H —H, —H —H, —H —H, —H 136 —H—H, —H —H, —H —H, —H —H, —H 137 —H —H, —H —H, —H —H, —H —H, —H 138 —H—H, —H —H, —H —H, —H —H, —H 139 —Cl —H, —H —H, —H —H, —H —H, —H 140 —H—H, —H —H, —H —H, —H —H, —H 141 —H —H, —H —H, —H —H, —H —H, —H 142 —H—H, —H —H, —H —H, —H —H, —H 143 —H —H, —H —H, —H —H, —H —H, —H 144 —H—H, —H —H, —H —H, —H —H, —H 145 —H —H, —H —H, —H —H, —H —H, —H

In the following Tables, introduction sites of respective substituents(R₁) and (R₂) are in an irregular order within the β-positionsubstitution type.

M-Pc(R₁)_(m)(R₂)_(n):

M-Pc(R₁)_(m)(R₂)_(n) Compound No. M R₁ m 146 Cu

3 147 Cu —SO₂—NH—CH₂—CH₂SO₃Li 3 148 Cu

3 149 Cu

2 150 Cu —SO₂—NH—CH₂—CH₂—SO₂—NH—CH₂CH₂—COONa 3 151 Cu

3 152 Cu

2.5 153 Cu

2 154 Cu —SO₂—CH₂—CH₂—CH₂—SO₃Li 3 155 Cu —SO₂—CH₂—CH₂—CH₂—COOK 2 156 Cu—SO₂—CH₂—CH₂—CH₂—SO₃Li 3 157 Cu —SO₂—CH₂—CH₂—O—CH₂—CH₂—SO₃Li 2 158 Cu

3 159 Cu —SO₂NHCH₂CH₂—SO₃Li 3 160 Cu—SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—SO₃Na 3 161 Cu —SO₂CH₂CH₂CH₂SO₃Li 3 162Cu —SO₂CH₂CH₂CH₂SO₃Li 2 163 Cu —SO₂CH₂CH₂CH₂SO₃K 3 164 Cu—SO₂CH₂CH₂CH₂SO₃Li 2 165 Cu —CO—NH—CH₂—CH₂—SO₃K 3 166 Cu—CO—NH—CH₂—CH₂—SO₂—NH—CH₂—CH₂—COONa 3 167 Cu

2.5 168 Cu

2 169 Cu —CO₂—CH₂—CH₂—CH₂—SO₃Li 3 170 Cu —CO₂—CH₂—CH₂—CH₂COOK 2 171 Cu—CO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—SO₃Na 3 172 Cu—SO₂CH₂CH₂OCH₂CH₂O—CH₂CH₂SO₃K 2 173 Cu

2 174 Cu

3 175 Cu —SO₂(CH₂)₃SO₂NH(CH₂)₃N(CH₂CH₂OH)₂ 2 176 Cu

3 177 Cu —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 2 178 Cu—SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—OH 3 179 Cu

2 180 Cu

3 181 Cu

3 182 Cu

2.5 183 Cu

2 184 Cu

3 185 Cu

3 186 Cu

3 187 Cu

3 188 Cu

3 189 Cu

3 190 Cu

3 Compound No. R₂ n 146

1 147

1 148 —SO₂NH—CH₂—CH₂—CH₂—SO₂—NH—CH₂—CH₂—O—CH₂—CH₂—OH 1 149

2 150

1 151 —SO₂NH—CH₂—CH₂—O—CH₂—CH₂—OH 1 152 —SO₂—CH₂—CH₂—O—CH₂—CH₂—OH 1.5153

2 154

1 155

2 156

1 157

2 158

1 159

1 160

1 161

1 162 —SO₂CH₂CH₂OCH₂CH₂OCH₂CH₂OH 2 163

1 164 —SO₂CH₂CH₂CH₂SO₂N(CH₂CH₂OH)₂ 2 165 —CO—NH—CH₂—CH₂—O—CH₂—CH₂—OH 1166

1 167

1.5 168

2 169

1 170

2 171

1 172

2 173

2 174

1 175

2 176

1 177

1 178

1 179

2 180 —SO₂NH—CH₂—CH₂—SO₂NH—CH₂—CH₂—O—CH₂—CH₂—OH 1 181

1 182

1.5 183 —SO₂—CH₂—CH₂—CH₂—SO₂—NH—(CH₂)₃—CH₂—O—CH₂CH₂—OH 2 184—SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 1 185—SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 1 186—SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—OH 1 187

1 188 —CO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 1 189

1 190 —CO—NH—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 1

The structure of the phthalocyanine compound represented byM-Pc(X_(p1))_(m)(X_(p2))_(n) in Compound Nos. 146 to 190 is shown below:

(wherein each X_(p1) is independently X_(p1) or X_(p2)).

The phthalocyanine dye represented by formula (I) can be synthesizedaccording to the patent publications described above. Furthermore, thephthalocyanine dye represented by formula (II) can be synthesized by themethods described in JP-A-2001-226275, JP-A-2001-96610, JP-A-2001-47013and JP-A-2001-193638 in addition to the above-described synthesismethod. The starting material, dye intermediate and synthesis route arenot limited to those described in these patent publications.

The inkjet recording ink having a main absorption region of 580 to 680nm for use in the present invention is preferably obtained by dissolvingor dispersing at least one phthalocyanine dye described above in anaqueous medium and in this case, the phthalocyanine dye is preferablycontained in an amount of 0.2 to 20 mass %, more preferably from 0.5 to15 mass %.

The ink of the present invention is preferably constituted to have atleast one of the following characteristic features 1) to 4) so as toprevent the image from blurring under high-humidity conditions:

1) at least two dyes represented by formula (I) are contained in oneink,

2) at least one dye represented by formula (I) and at least one dyeother than the dye represented by formula (I) are contained in one ink,

3) two or more inks are used in combination as an ink set, each inkcontains dyes differing in the structure and at least one ink containsat least a dye represented by formula (I), where the dyes differing inthe structure may be two dyes represented by formula (I) or may be a dyerepresented by formula (I) and a dye other than that, and

4) two or more inks are used in combination as an ink set and each inkcontains common dyes differing in the concentration, where the commondyes are preferably a dye represented by formula (I).

In the present invention, the dye for the inkjet recording ink having amain absorption region of 580 to 680 nm is preferably a substantiallywater-soluble or water-dispersible dye. More specifically, thesolubility of the coloring material in water at 20° C. is preferably 2mass % or more, more preferably 5 mass % or more. In the case of thephthalocyanine dyes represented by formula (I) for use in the presentinvention, the solubility of coloring material in water at 20° C. ispreferably 2 mass % or more.

When two or more inks are used in combination as a set, the dyecontained in each ink may be a single dye or a mixture of dyes. In thecase of a mixture of dyes, the ink containing the dye represented byformula (I) of the present invention preferably contains the dyerepresented by formula (I) in an amount of at least 10 mass % or more.

In preparing an ink set comprising two or more inks, generally, one inkis produced as a light-type thin ink and another is produced as a thickink, but in the present invention, the inks may be produced as differenttype inks in this way or may be produced as inks having almost the sameconcentration.

In the magenta ink having a main spectral absorption region of 500 to580 nm and the cyan ink having a main spectral adsorption region of 580to 680 nm for use in the present invention, in addition to theabove-described specific dye of formula (1) or (I) preferred in thepresent invention, other dyes can be added for the purpose of, forexample, adjusting the color tone. As for the dye which can be usedtogether in addition to the dye represented by formula (1) or (I), dyesknown in this field such as triarylmethane dye, anthraquinone dye,anthrapyridone dye, azomethine dye, azo dye, cyanine dye, merocyaninedye and oxonol dye can be used individually or in combination.

Also, for constituting an ink set for full color printing, other inkssuch as yellow ink and black ink are used in combination with themagenta and cyan inks of the present invention and in these inks,respective coloring matters are used.

Examples of the coloring matter which can be used in the same ink or inthe ink combined include the followings.

Examples of the yellow dye include aryl- or heteryl-azo dyes having aphenol, a naphthol, an aniline, a pyrazolone, a pyridone or an openchain-type active methylene compound as the coupling component;azomethine dyes having an open chain-type active methylene compound asthe coupling component; methine dyes such as benzylidene dye andmonomethine oxonol dye; and quinone-base dyes such as naphthoquinone dyeand anthraquinone dye. Other examples of the dye species includequinophthalone dye, nitro•nitroso dye, acridine dye and acridinone dye.These dyes may be a dye which provides a yellow color for the first timewhen a part of the chromophore is dissociated. In this case, the countercation may be an inorganic cation such as alkali metal and ammonium, anorganic cation such as pyridinium and quaternary ammonium salt, or apolymer cation having such a cation in the partial structure.

Examples of the magenta dye include aryl- or heteryl-azo dyes having aphenol, a naphthol or an aniline as the coupling component; azomethinedyes having a pyrazolone or a pyrazolotriazole as the couplingcomponent; methine dyes such as arylidene dye, styryl dye, merocyaninedye and oxonol dye; carbonium dyes such as diphenylmethane dye,triphenylmethane dye and xanthene dye; quinone-base dyes such asnaphthoquinone, anthraquinone and anthrapyridone; and condensedpolycyclic dyes such as dioxazine dye. These dyes may be a dye whichprovides a magenta color for the first time when a part of thechromophore is dissociated. In this case, the counter cation may be aninorganic cation such as alkali metal and ammonium, an organic cationsuch as pyridinium and quaternary ammonium salt, or a polymer cationhaving such a cation in the partial structure.

Examples of the cyan dye include azomethine dyes such as indoaniline dyeand indophenol dye; polymethine dyes such as cyanine dye, oxonol dye andmerocyanine dye; carbonium dyes such as diphenylmethane dye,triphenylmethane dye and xanthene dye; phthalocyanine dyes;anthraquinone dyes; aryl- or heteryl-azo dyes having a phenol, anaphthol or an aniline as the coupling component; and indigo•thioindigodyes. These dyes may be a dye which provides a cyan color for the firsttime when a part of the chromophore is dissociated. In this case, thecounter cation may be an inorganic cation such as alkali metal andammonium, an organic cation such as pyridinium and quaternary ammoniumsalt, or a polymer cation having such a cation in the partial structure.

A black dye such as polyazo dye can also be used.

Examples of the water-soluble dye include a direct dye, an acid dye, afood color, a basic dye and a reactive dye. Preferred examples thereofinclude C.I. Direct Red 2, 4, 9, 23, 26, 31, 39, 62, 63, 72, 75, 76, 79,80, 81, 83, 84, 89, 92, 95, 111, 173, 184, 207, 211, 212, 214, 218, 21,223, 224, 225, 226, 227, 232, 233, 240, 241, 242, 243 and 247; C.I.Direct Violet 7, 9, 47, 48, 51, 66, 90, 93, 94, 95, 98, 100 and 101;C.I. direct Yellow 8, 9, 11, 12, 27, 28, 29, 33, 35, 39, 41, 44, 50, 53,58, 59, 68, 86, 87, 93, 95, 96, 98, 100, 106, 108, 109, 110, 130, 132,142, 144, 161 and 163; C.I. Direct Blue 1, 10, 15, 22, 25, 55, 67, 68,71, 76, 77, 78, 80, 84, 86, 87, 90, 98, 106, 108, 109, 151, 156, 158,159, 160, 168, 189, 192, 193, 194, 199, 200, 201, 202, 203, 207, 211,213, 214, 218, 225, 229, 236, 237, 244, 248, 249, 251, 252, 264, 270,280, 288, 289 and 291; C.I. Direct Black 9, 17, 19, 22, 32, 51, 56, 62,69, 77, 80, 91, 94, 97, 108, 112, 113, 114, 117, 118, 121, 122, 125,132, 146, 154, 166, 168, 173 and 199; C.I. Acid Red 35, 42, 52, 57, 62,80, 82, 111, 114, 118, 119, 127, 128, 131, 143, 151, 154, 158, 249, 254,257, 261, 263, 266, 289, 299, 301, 305, 336, 337, 361, 396 and 397; C.I.Acid Violet 5, 34, 43, 47, 48, 90, 103 and 126; C.I. Acid Yellow 17, 19,23, 25, 39, 40, 42, 44, 49, 50, 61, 64, 76, 79, 110, 127, 135, 143, 151,159, 169, 174, 190, 195, 196, 197, 199, 218, 219, 222 and 227; C.I. AcidBlue 9, 25, 40, 41, 62, 72, 76, 78, 80, 82, 92, 106, 112, 113, 120,127:1, 129, 138, 143, 175, 181, 205, 207, 220, 221, 230, 232, 247, 258,260, 264, 271, 277, 278, 279, 280, 288, 290 and 326; C.I. Acid Black 7,24, 29, 48, 52:1 and 172; C.I. Reactive Red 3, 13, 17, 19, 21, 22, 23,24, 29, 35, 37, 40, 41, 43, 45, 49 and 55; C.I. Reactive Violet 1, 3, 4,5, 6, 7, 8, 9, 16, 17, 22, 23, 24, 26, 27, 33 and 34; C.I. ReactiveYellow 2, 3, 13, 14, 15, 17, 18, 23, 24, 25, 26, 27, 29, 35, 37, 41 and42; C.I. Reactive Blue 2, 3, 5, 8, 10, 13, 14, 15, 17, 18, 19, 21, 25,26, 27, 28, 29 and 38; C.I. Reactive Black 4, 5, 8, 14, 21, 23, 26, 31,32 and 34; C.I. Basic Red 12, 13, 14, 15, 18, 22, 23, 24, 25, 27, 29,35, 36, 38, 39, 45 and 46; C.I. Basic Violet 1, 2, 3, 7, 10, 15, 16, 20,21, 25, 27, 28, 35, 37, 39, 40 and 48; C.I. Basic Yellow 1, 2, 4, 11,13, 14, 15, 19, 21, 23, 24, 25, 28, 29, 32, 36, 39 and 40; C.I. BasicBlue 1, 3, 5, 7, 9, 22, 26, 41, 45, 46, 47, 54, 57, 60, 62, 65, 66, 69and 71; and C.I. Basic Black 8.

In the ink composition of the present invention, for adjusting the colortone so as to obtain a full color image, other coloring materials can beused together with the above-described dye. Examples of the othercoloring material which can be used together include the followingpigments.

As the pigment for use in the present invention, commercially availablepigments and known pigments described in various publications can beused. Examples of the publication include Color Index, compiled by TheSociety of Dyers and Colourists, Kaitei Shin Han Ganryo Binran (RevisedNew Handbook of Pigments), compiled by Nippon Ganryo Gijutsu Kyokai(1989), Saishin Ganryo Oyo Gijutsu (Newest Pigment ApplicationTechnology), CMC Shuppan (1986), Insatsu Ink Gijutsu (Printing InkTechnique), CMC Shuppan (1984), and W. Herbst and K. Hunger, IndustrialOrganic Pigments, VCH Verlagsgesellschaft (1993). Specific examples ofthe pigment include organic pigments such as azo pigments (e.g., azolake pigment, insoluble azo pigment, condensed azo pigment, chelate azopigment), polycyclic pigments (e.g., phthalocyanine-base pigment,anthraquinone-base pigment, perylene-base or perynone-base pigment,indigo-base pigment, quinacridone-base pigment, dioxazine-base pigment,isoindolinone-base pigment, quinophthalone-base pigment,diketopyrrolopyrrole-base pigment), dyeing lake pigments (lake pigmentsof acidic or basic dye) and azine pigments, and inorganic pigments suchas C.I. Pigment Yellow 34, 37, 42 and 53 which are a yellow pigment,C.I. Pigment Red 101 and 108 which are a red-type pigment, C.I. PigmentBlue 27, 29 and 17:1 which are a blue-type pigment, C.I. Pigment Black 7and magnetite which are a black-type pigment, and C.I. Pigment White 4,6, 18 and 21 which are a white-type pigment.

The pigment having a color tone preferred for the formation of an imageincludes the followings. As the blue to cyan pigment, phthalocyaninepigments, anthraquinone-type indanthrone pigments (for example, C.I.Pigment Blue 60) and dyeing lake pigment-type triarylcarbonium pigmentsare preferred, and phthalocyanine pigments are most preferred (preferredexamples thereof include copper phthalocyanine such as C.I. Pigment Blue15:1, 15:2, 15:3, 15:4 and 15:6, monochloro or low chlorinated copperphthalocyanine, aluminum phthalocyanine such as pigments described inEuropean Patent 860475, nonmetallic phthalocyanine such as C.I. PigmentBlue 16, and phthalocyanine with the center metal being Zn, Ni or Ti,and among these, C.I. Pigment Blue 15:3 and 15:4 and aluminumphthalocyanine are more preferred).

As the red to violet pigment, azo pigments (preferred examples thereofinclude C.I. Pigment Red 3, 5, 11, 22, 38, 48:1, 48:2, 48:3, 48:4, 49:1,52:1, 53:1, 57:1, 63:2, 144, 146 and 184, and among these, C.I. PigmentRed 57:1, 146 and 184 are more preferred), quinacridone-base pigments(preferred examples thereof include C.I. Pigment Red 122, 192, 202, 207and 209 and C.I. Pigment Violet 19 and 42, and among these, C.I. PigmentRed 122 is more preferred), dyeing lake pigment-type triarylcarboniumpigments (preferred examples thereof include xanthene-base C.I. PigmentRed 81:1 and C.I. Pigment Violet 1, 2, 3, 27 and 39), dioxazine-basepigments (for example, C.I. Pigment Violet 23 and 37),diketopyrrolopyrrole-base pigments (for example, C.I. Pigment Red 254),perylene pigments (for example, C.I. Pigment Violet 29),anthraquinone-base pigments (for example, C.I. Pigment Violet 5:1, 31and 33) and thioindigo-base pigments (for example, C.I. Pigment Red 38and 88) are preferred.

As the yellow pigment, azo pigments (preferred examples thereof includemonoazo pigment-type C.I. Pigment Yellow 1, 3, 74 and 98, disazopigment-type C.I. Pigment Yellow 12, 13, 14, 16, 17 and 83, syntheticazo-type C.I. Pigment 93, 94, 95, 128 and 155, and benzimidazolone-typeC.I. Pigment Yellow 120, 151, 154, 156 and 180, and among these, thosenot using a benzidine-base compound as a raw material are morepreferred), isoindoline-isoindolinone-base pigments (preferred examplesthereof include C.I. Pigment Yellow 109, 110, 137 and 139),quinophthalone pigments (preferred examples thereof include C.I. PigmentYellow 138) and flavanthrone pigments (for example, C.I. Pigment Yellow24) are preferred.

As the black pigment, inorganic pigments (preferred examples thereofinclude carbon black and magnetite) and aniline black are preferred.

Other than these, an orange pigment (for example, C.I. Pigment Orange 13and 16) and a green pigment (for example, C.I. Pigment Green 7) may beused.

The above-described pigment which can be used in the present inventionmay be used as it is or may be subjected to a surface treatment. For thesurface treatment, a method of coating the surface with resin or wax, amethod of attaching a surfactant, and a method of binding a reactivesubstance (for example, a radical generated from a silane couplingagent, an epoxy compound, polyisocyanate or a diazonium salt) to thepigment surface may be used and these are described in the followingpublications and patents:

(1) Kinzoku Sekken no Seishitsu to Oyo (Properties and Applications ofMetal Soap), Saiwai Shobo;

(2) Insatsu Ink Insatsu (Printing Ink Printing), CMC Shuppan (1984);

(3) Saishin Ganryo Oyo Gijutsu (Newest Pigment Application Technology),CMC Shuppan (1986);

(4) U.S. Pat. Nos. 5,554,739 and 5,571,311; and

(5) JP-A-9-151342, JP-A-10-140065, JP-A-10-292143 and JP-A-11-166145.

Particularly, self-dispersible pigments prepared by allowing a diazoniumsalt to act on carbon black described in U.S. patents of (4) andcapsulated pigments prepared by the method described in Japanese patentpublications of (5) are effective, because dispersion stability can beobtained without using an excess dispersant in the ink.

In the present invention, the pigment may be dispersed by further usinga dispersant. Various known dispersants can be used according to thepigment used, for example, a surfactant-type low molecular dispersant ora polymer-type dispersant can be used. Examples of the dispersantinclude those described in JP-A-3-69949 and European Patent 549486. Inusing the dispersant, a pigment derivative called synergist may also beadded so as to accelerate the adsorption of dispersant to the pigment.

The particle size of the pigment which can be used in the presentinvention is, after dispersion, preferably from 0.01 to 10 μm, morepreferably from 0.05 to 1 μm.

As for the method of dispersing the pigment, known dispersion techniquesused for the production of ink or toner can be used. Examples of thedispersing machine include vertical or horizontal agitator mill,attritor, colloid mill, ball mill, three-roll mill, pearl mill,super-mill, impeller, disperser, KD mill, dynatron and pressure kneader.These are described in detail in Saishin Ganryo Oyo Gijutsu (NewestPigment Application Technology), CMC Shuppan (1986).

Other components which can be contained in the inkjet recording inkcomposition of the present invention are described below.

The inkjet recording ink of the present invention may contain asurfactant. By containing a surfactant, the liquid properties of ink arecontrolled and this can provide excellent effects such as enhancement ofejection stability of ink, improvement of water resistance of image, andprevention of bleeding of printed ink.

Examples of the surfactant include anionic surfactants such as sodiumdodecylsulfate, sodium dodecyloxysulfonate and sodiumalkylbenzenesulfonate, cationic surfactants such as cetylpyridiniumchloride, trimethylcetylammonium chloride and tetrabutylammoniumchloride, and nonionic surfactants such as polyoxyethylene nonylphenylether, polyoxyethylene naphthyl ether and polyoxyethylene octylphenylether. Among these, nonionic surfactants are preferred.

The surfactant content in the ink is from 0.001 to 15 mass %, preferablyfrom 0.005 to 10 mass %, more preferably from 0.01 to 5 mass %.

The inkjet recording ink of the present invention can be prepared bydissolving and/or dispersing the above-described phthalocyanine dye andthe surfactant in an aqueous medium. The term “aqueous medium” as usedin the present invention means water or a mixture of water and a smallamount of water-miscible organic solvent, where additives such aswetting agent, stabilizer and antiseptic are added, if desired.

Examples of the water-miscible organic solvent which can be used in thepresent invention include alcohols (e.g., methanol, ethanol, propanol,isopropanol, butanol, isobutanol, sec-butanol, tert-butanol, pentanol,hexanol, cyclohexanol, benzyl alcohol), polyhydric alcohols (e.g.,ethylene glycol, diethylene glycol, triethylene glycol, polyethyleneglycol, propylene glycol, dipropylene glycol, polypropylene glycol,butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol,thiodiglycol), glycol derivatives (e.g., ethylene glycol monomethylether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether,diethylene glycol monomethyl ether, diethylene glycol monobutyl ether,propylene glycol monomethyl ether, propylene glycol monobutyl ether,dipropylene glycol monomethyl ether, triethylene glycol monomethylether, ethylene glycol diacetate, ethylene glycol monomethyl etheracetate, triethylene glycol monomethyl ether, triethylene glycolmonoethyl ether, ethylene glycol monophenyl ether), amines (e.g.,ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine,N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine,diethylenetriamine, triethylenetetramine, polyethyleneimine,tetramethylpropylenediamine) and other polar solvents (e.g., formamide,N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide,sulfolane, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone,2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, acetonitrile, acetone).These water-miscible organic solvents can be used in combination of twoor more thereof.

In the case where the phthalocyanine dye or other dye which can be usedin the present invention is an oil-soluble dye, the ink can be preparedby dissolving the oil-soluble dye in a high boiling point organicsolvent and emulsion-dispersing it in an aqueous medium.

The high boiling point organic solvent for use in the present inventionhas a boiling point of 150° C. or more, preferably 170° C. or more.

Examples of the high boiling point organic solvent include phthalic acidesters (e.g., dibutyl phthalate, dioctyl phthalate, dicyclohexylphthalate, di-2-ethylhexyl phthalate, decyl phthalate,bis(2,4-di-tert-amylphenyl) isophthalate, bis(1,1-diethylpropyl)phthalate), esters of phosphoric acid or phosphone (e.g., diphenylphosphate, triphenyl phosphate, tricresyl phosphate,2-ethylhexyldiphenyl phosphate, dioctylbutyl phosphate, tricyclohexylphosphate, tri-2-ethylhexyl phosphate, tridodecyl phosphate,di-2-ethylhexylphenyl phosphate), benzoic acid esters (e.g.,2-ethylhexyl benzoate, 2,4-dichlorobenzoate, dodecyl benzoate,2-ethylhexyl-p-hydroxybenzoate), amides (e.g., N,N-diethyldodecanamide,N,N-diethyllaurylamide), alcohols or phenols (e.g., isostearyl alcohol,2,4-di-tert-amylphenol), aliphatic esters (e.g., dibutoxyethylsuccinate, di-2-ethylhexyl succinate, 2-hexyldecyl tetradecanoate,tributyl citrate, diethyl azelate, isostearyl lactate, trioctylcitrate), aniline derivatives (e.g.,N,N-dibutyl-2-butoxy-5-tertoctylaniline), chlorinated paraffins (e.g.,paraffins having a chlorine content of 10 to 80%), trimesic acid esters(e.g., tributyl trimesate), dodecylbenzene, diisopropylnaphthalene,phenols (e.g., 2,4-di-tert-amylphenol, 4-dodecyloxyphenol,4-dodecyloxycarbonylphenol, 4-(4-dodecyloxyphenylsulfonyl)phenol),carboxylic acids (e.g., 2-(2,4-di-tert-amylphenoxy)butyric acid,2-ethoxyoctanedecanoic acid) and alkylphosphoric acids (e.g.,di-(2-ethylhexyl)phosphoric acid and diphenylphosphoric acid). The highboiling point organic solvent can be used in an amount of, in terms ofmass ratio to the oil-soluble dye, from 0.01 to 3 times, preferably from0.01 to 1.0 times.

These high boiling point organic solvents may be used individually or asa mixture of several kinds [for example, tricresyl phosphate and dibutylphthalate, trioctyl phosphate and di(2-ethylhexyl) sebacate, or dibutylphthalate and poly(N-tert-butylacrylamide)].

Examples of the high boiling point organic solvent for use in thepresent invention, other than the above-described compounds, and/or thesynthesis method of these high boiling point organic solvents aredescribed in U.S. Pat. Nos. 2,322,027, 2,533,514, 2,772,163, 2,835,579,3,594,171, 3,676,137, 3,689,271, 3,700,454, 3,748,141, 3,764,336,3,765,897, 3,912,515, 3,936,303, 4,004,928, 4,080,209, 4,127,413,4,193,802, 4,207,393, 4,220,711, 4,239,851, 4,278,757, 4,353,979,4,363,873, 4,430,421, 4,430,422, 4,464,464, 4,483,918, 4,540,657,4,684,606, 4,728,599, 4,745,049, 4,935,321 and 5,013,639, EP-A-276319,EP-A-286253, EP-A-289820, EP-A-309158, EP-A-309159, EP-A-309160,EP-A-509311, EP-A-510576, East German Patents 147,009, 157,147, 159,573and 225,240A, British Patent 2091124A, JP-A-48-47335, JP-A-50-26530,JP-A-51-25133, JP-A-51-26036, JP-A-51-27921, JP-A-51-27922,JP-A-51-149028, JP-A-52-46816, JP-A-53-1520, JP-A-53-1521,JP-A-53-15127, JP-A-53-146622, JP-A-54-91325, JP-A-54-106228,JP-A-54-118246, JP-A-55-59464, JP-A-56-64333, JP-A-56-81836,JP-A-59-204041, JP-A-61-84641, JP-A-62-118345, JP-A-62-247364,JP-A-63-167357, JP-A-63-214744, JP-A-63-301941, JP-A-64-9452,JP-A-64-9454, JP-A-64-68745, JP-A-1-101543, JP-A-1-102454, JP-A-2-792,JP-A-2-4239, JP-A-2-43541, JP-A-4-29237, JP-A-4-30165, JP-A-4-232946 andJP-A-4-346338.

The high boiling point organic solvent is used in an amount of, in termsof mass ratio to the oil-soluble dye, from 0.01 to 3.0 times, preferablyfrom 0.01 to 1.0 times.

In the present invention, the oil-soluble dye or high boiling pointorganic solvent is used by emulsion-dispersing it in an aqueous medium.Depending on the case, a low boiling point organic solvent may be usedat the emulsion-dispersion in view of emulsifiability. The low boilingpoint organic solvent is an organic solvent having a boiling point ofabout 30 to 150° C. under atmospheric pressure. Preferred examplesthereof include, but are not limited to, esters (e.g., ethyl acetate,butyl acetate, ethyl propionate, β-ethoxyethyl acetate, methylcellosolveacetate), alcohols (e.g., isopropyl alcohol, n-butyl alcohol, secondarybutyl alcohol), ketones (e.g., methyl isobutyl ketone, methyl ethylketone, cyclohexanone), amides (e.g., dimethylformamide,N-methylpyrrolidone) and ethers (e.g., tetrahydrofuran, dioxane).

In the emulsion-dispersion, an oil phase obtained by dissolving the dyein a high boiling organic solvent or depending on the case, in a mixedsolvent of a high boiling organic solvent and a low boiling organicsolvent is dispersed in an aqueous phase mainly comprising water to formfine oil droplets of the oil phase. At this time, in either one or bothof the aqueous phase and the oil phase, additives described later, suchas surfactant, wetting agent, dye stabilizer, emulsification stabilizer,antiseptic and fungicide, can be added, if desired.

In the general emulsification method, an oil phase is added to anaqueous phase, but a so-called phase inversion emulsification method ofadding dropwise an aqueous phase in an oil phase can also be preferablyused.

In performing the emulsion-dispersion of the present invention, varioussurfactants can be used. Preferred examples thereof include anionicsurfactants such as fatty acid salt, alkylsulfuric ester salt,alkylbenzenesulfonate, alkylnaphthalenesulfonate, dialkylsulfosuccinate,alkylphosphoric ester salt, naphthalenesulfonic acid formalin condensateand polyoxyethylene alkylsulfuric ester salt, and nonionic surfactantssuch as polyoxyethylene alkyl ether, polyoxyethylene alkylallyl ether,polyoxyethylene fatty acid ester, sorbitan fatty acid ester,polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylamine,glycerin fatty acid ester and oxyethylene oxypropylene block copolymer.Also, SURFYNOLS (produced by Air Products & Chemicals), which are anacetylene-base polyoxyethylene oxide surfactant, are preferably used.Furthermore, amine oxide-type amphoteric surfactants such asN,N-dimethyl-N-alkylamine oxide are preferred. In addition, surfactantsdescribed in JP-A-59-157636 (pages (37) to (38)) and ResearchDisclosure, No. 308119 (1989) can also be used.

For the purpose of stabilizing the dispersion immediately afteremulsification, a water-soluble polymer may be added in combination withthe surfactant. Preferred examples of the water-soluble polymer includepolyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide, polyacrylicacid, polyacrylamide and copolymers thereof. Other than these, naturalwater-soluble polymers such as polysaccharides, casein and gelatin arealso preferably used. Furthermore, for the stabilization of dyedispersion, a polymer which does not substantially dissolve in anaqueous medium, such as polyvinyl, polyurethane, polyester, polyamide,polyurea and polycarbonate obtained by the polymerization of acrylicacid esters, methacrylic acid esters, vinyl esters, acrylamides,methacrylamides, olefins, styrenes, vinyl ethers or acrylonitriles, canalso be used in combination. This polymer preferably contains —SO²⁻ or—COO⁻. In the case of using this polymer which does not substantiallydissolve in an aqueous medium, the polymer is preferably used in anamount of 20 mass % or less, more preferably 10 mass % or less, based onthe high boiling point organic solvent.

In preparing an aqueous ink by dispersing the oil-soluble dye or highboiling point organic solvent according to emulsion-dispersion, thecontrol of particle size is important. In order to elevate the colorpurity or density of an image formed by the inkjet recording, it isessential to reduce the average particle size. The average particle sizeis, in terms of the volume average particle size, preferably 1 μm orless, more preferably from 5 to 100 nm.

The volume average particle size and particle size distribution of thedispersed particles can be easily measured by a known method such asstatic light scattering method, dynamic light scattering method,centrifugal precipitation method and the method described in JikkenKagaku Koza (Lecture of Experimental Chemistry), 4th ed., pp. 417–418.For example, the ink is diluted with distilled water to have a particleconcentration of 0.1 to 1 mass %, then, the particle size can be easilymeasured by a commercially available volume average particle sizemeasuring apparatus (for example, Microtrac UPA (manufactured by NikkisoK.K.)). The dynamic light scattering method utilizing the laser Dopplereffect is particularly preferred because even a small particle size canbe measured.

The volume average particle size is an average particle size weightedwith the particle volume and is obtained by multiplying the diameter ofindividual particles in the gathering of particles by the volume of theparticle and dividing the sum total of the obtained values by the totalvolume of the particles. The volume average particle size is describedin Soichi Muroi, Kobunshi Latex no Kagaku (Chemistry of Polymer Latex),page 119, Kobunshi Kanko Kai.

Also, it is revealed that the presence of coarse particles greatlyaffects the printing performance. More specifically, the coarse particleclogs the nozzle of head or even if the nozzle is not clogged, forms asoil to bring about ejection failure or ejection slippage of ink andthis seriously affects the printing performance. In order to preventthese troubles, it is important to reduce the number of particles havinga particle size of 5 μm or more to 10 or less and the number ofparticles having a particle size of 1 μm or more to 1,000 or less, in 1μl of ink prepared.

For removing these coarse particles, a known method such as centrifugalseparation or microfiltration can be used. This separation step may beperformed immediately after the emulsion-dispersion or may be performedimmediately before filling the ink in an ink cartridge after variousadditives such as wetting agent and surfactant are added to theemulsified dispersion.

A mechanically emulsifying apparatus is effective for reducing theaverage particle size and eliminating coarse particles.

As for the emulsifying apparatus, known apparatuses such as simplestirrer, impeller stirring system, in-line stirring system, mill system(e.g., colloid mill) and ultrasonic system can be used, but ahigh-pressure homogenizer is particularly preferred.

The mechanism of the high-pressure homogenizer is described in detail inU.S. Pat. No. 4,533,254 and JP-A-6-47264. Examples of the commerciallyavailable apparatus include Gaulin Homogenizer (manufactured by A.P.VGaulin Inc.), Microfluidizer (manufactured by Microfluidex Inc.) andAltimizer (produced by Sugino Machine).

The high-pressure homogenizer with a mechanism of pulverizing particlesin an ultrahigh pressure jet stream recently described in U.S. Pat. No.5,720,551 is particularly effective for the emulsion-dispersion of thepresent invention. Examples of the emulsifying apparatus using thisultrahigh pressure jet stream include DeBEE2000 (manufactured by BEEInternational Ltd.).

In performing the emulsification by a high-pressure emulsion-dispersingapparatus, the pressure is 50 MPa or more, preferably 60 MPa or more,more preferably 180 MPa or more.

A method of using two or more emulsifying apparatuses, for example, byperforming the emulsification in a stirring emulsifier and then passingthe emulsified product through a high-pressure homogenizer isparticularly preferred. In addition, a method of once performing theemulsion-dispersion by such an emulsifying apparatus and after addingadditives such as wetting agent and surfactant, again passing thedispersion through a high-pressure homogenizer during filling of the inkinto a cartridge is also preferred.

In the case of containing a low boiling point organic solvent inaddition to the high boiling point organic solvent, the low boilingpoint solvent is preferably removed in view of stability of theemulsified product, safety and hygiene. For removing the low boilingpoint solvent, various known methods can be used according to the kindof the solvent, such as evaporation, vacuum evaporation andultrafiltration. This removal of the low boiling point organic solventis preferably performed as soon as possible immediately after theemulsification.

In the inkjet recording ink of the present invention, additives such asdrying inhibitor for preventing clogging due to drying of ink at theejection port, penetration accelerator for more successfully penetratingthe ink into paper, ultraviolet absorbent, antioxidant, viscosityadjusting agent, surface tension adjusting agent, dispersant, dispersionstabilizer, fungicide, rust inhibitor, pH adjusting agent, defoamingagent and chelating agent, may be appropriately selected and used in anappropriate amount.

The drying inhibitor for use in the present invention is preferably awater-soluble organic solvent having a vapor pressure lower than water.Specific examples thereof include polyhydric alcohols as represented byethylene glycol, propylene glycol, diethylene glycol, polyethyleneglycol, thiodiglycol, dithiodiglycol, 2-methyl-1,3-propanediol,1,2,6-hexanetriol, acetylene glycol derivative, glycerin andtrimethylolpropane; lower alkyl ethers of polyhydric alcohol, such asethylene glycol monomethyl(or ethyl) ether, diethylene glycolmonomethyl(or ethyl) ether and triethylene glycol monoethyl(or butyl)ether; heterocyclic rings such as 2-pyrrolidone, N-methyl-2-pyrrolidone,1,3-dimethyl-2-imidazolidinone and N-ethylmorpholine; sulfur-containingcompounds such as sulfolane, dimethylsulfoxide and 3-sulfolene;polyfunctional compounds such as diacetone alcohol and diethanolamine;and urea derivatives. Among these, polyhydric alcohols such as glycerinand diethylene glycol are preferred. These drying inhibitors may be usedindividually or in combination of two or more thereof. In the ink, thedrying inhibitor is preferably contained in an amount of 10 to 50 mass%.

Examples of the penetration accelerator which can be used in the presentinvention include alcohols such as ethanol, isopropanol, butanol,di(tri)ethylene glycol monobutyl ether and 1,2-hexanediol, sodiumlaurylsulfate, sodium oleate and nonionic surfactants. A sufficientlyhigh effect can be obtained by adding from 10 to 30 mass % of thepenetration accelerator in the ink. The penetration accelerator ispreferably used in an amount of causing no blurring of printed letter orno print through.

Examples of the ultraviolet absorbent which can be used in the presentinvention for improving the preservability of image includebenzotriazole-base compounds described in JP-A-58-185677,JP-A-61-190537, JP-A-2-782, JP-A-5-197075 and JP-A-9-34057,benzophenone-base compounds described in JP-A-46-2784, JP-A-5-194483 andU.S. Pat. No. 3,214,463, cinnamic acid-base compounds described inJP-B-48-30492 (the term “JP-B” as used herein means an “examinedJapanese patent publication”), JP-B-56-21141 and JP-A-10-88106,triazine-base compounds described in JP-A-4-298503, JP-A-8-53427,JP-A-8-239368, JP-A-10-182621 and JP-T-8-501291, compounds described inResearch Disclosure No. 24239, and compounds of absorbing ultravioletlight and emitting fluorescent light, so-called fluorescent brighteningagents, as represented by stilbene-base compounds and benzoxazole-basecompounds.

As for the antioxidant which is used in the present invention forimproving the preservability of image, various organic or metalcomplex-base discoloration inhibitors can be used. Examples of theorganic discoloration inhibitor include hydroquinones, alkoxyphenols,dialkoxyphenols, phenols, anilines, amines, indanes, chromans,alkoxyanilines and heterocyclic rings. Examples of the metal complexinclude nickel complex and zinc complex. More specifically, compoundsdescribed in patents cited in Research Disclosure, Nos. 17643 (ItemsVII-I to VII-J), 15162, 18716 (page 650, left column), 36544 (page 527),307105 (page 872) and 15162, and compounds included in formulae ofrepresentative compounds and in exemplary compounds described inJP-A-62-215272 (pages 127 to 137) can be used.

Examples of the fungicide for use in the present invention includesodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide,ethyl p-hydroxybenzoate, 1,2-benzisothiazolin-3-one and salts thereof.In the ink, the fungicide is preferably used in an amount of 0.02 to5.00 mass %.

The fungicide is described in detail, for example, in Bokin Bobai ZaiJiten (Dictionary of Microbicide and Fungicide), compiled by NipponBokin Bobai Gakkai Jiten Henshu Iinkai.

Examples of the rust inhibitor include acidic sulfite, sodiumthiosulfate, ammonium thioglycolate, diisopropylammonium nitrite,pentaerythritol tetranitrate, dicyclohexylammonium nitrite andbenzotriazole. In the ink, the rust inhibitor is preferably used in anamount of 0.02 to 5.00 mass %.

The pH adjusting agent for use in the present invention can be suitablyused for adjusting the pH and imparting dispersion stability. The pH ofthe ink is preferably adjusted to 8 to 11 at 25° C. If the pH is lessthan 8, the solubility of dye decreases to readily cause clogging of anozzle, whereas if it exceeds 11, the water resistance tends todeteriorate. Examples of the pH adjusting agent include organic basesand inorganic alkalis for giving a basic pH, and organic acids andinorganic acids for giving an acidic pH.

Examples of the organic base include triethanolamine, diethanolamine,N-methyldiethanolamine and dimethylethanolamine. Examples of theinorganic alkali include alkali metal hydroxides (e.g., sodiumhydroxide, lithium hydroxide, potassium hydroxide), alkali metalcarbonates (e.g., sodium carbonate, sodium hydrogencarbonate) andammonium. Examples of the organic acid include an acetic acid, apropionic acid, a trifluoroacetic acid and an alkylsulfonic acid.Examples of the inorganic acid include a hydrochloric acid, a sulfuricacid and a phosphoric acid.

In the present invention, apart from the above-described surfactants, anonionic, cationic or anionic surfactant is used as the surface tensionadjusting agent. Examples thereof include anionic surfactants such asfatty acid salt, alkylsulfuric ester salt, alkylbenzenesulfonate,alkylnaphthalenesulfonate, dialkylsulfosuccinate, alkylphosphoric estersalt, naphthalenesulfonic acid formalin condensate andpolyoxyethylenealkylsulfuric ester salt, and nonionic surfactants suchas polyoxyethylene alkyl ether, polyoxyethylene alkylallyl ether,polyoxyethylene fatty acid ester, sorbitan fatty acid ester,polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylamine,glycerin fatty acid ester and oxyethylene oxypropylene block copolymer.Also, SURFYNOLS (produced by Air Products & Chemicals), which are anacetylene-base polyoxyethylene oxide surfactant, are preferably used.Furthermore, amine oxide-type amphoteric surfactants such asN,N-dimethyl-N-alkylamine oxide are preferred. In addition, surfactantsdescribed in JP-A-59-157636 (pages (37) to (38)) and ResearchDisclosure, No. 308119 (1989) can also be used.

The surface tension of the ink of the present invention is, with orwithout use of such a surface tension adjusting agent, preferably from20 to 60 mN/m, more preferably from 25 to 45 mN/m.

The ink of the present invention preferably has a viscosity of 30 mPa·sor less. The viscosity is more preferably adjusted to 20 mPa·s or less.For the purpose of adjusting the viscosity, a viscosity adjusting agentis sometimes used. Examples of the viscosity adjusting agent includewater-soluble polymers such as celluloses and polyvinyl alcohol, andnonionic surfactants. The viscosity adjusting agent is described indetail in Nendo Chosei Gijutsu (Viscosity Adjusting Technology), Chap.9, Gijutsu Joho Kyokai (1999), and Inkjet Printer Yo Chemicals (98Zoho)—Zairyo no Kaihatsu Doko•Tenbo Chosa—(Chemicals for Inkjet Printer(Enlarged Edition of 98)—Survey on Development Tendency•Prospect ofMaterials—), pp. 162–174, CMC (1997).

In the present invention, if desired, various cationic, anionic ornonionic surfactants described above may be used as a dispersant or adispersion stabilizer, and fluorine- or silicone-base compounds orchelating agents as represented by EDTA may be used as a defoamingagent.

In preparing the ink solution of the present invention, in the case of awater-soluble ink, the dye is preferably first dissolved in water andthereafter, various solvents and additives are added, dissolved andmixed to provide a uniform ink solution.

For dissolving the dye and the like, various methods such as stirring,ultrasonic irradiation and shaking can be used. Among these, stirring ispreferred. In performing the stirring, various systems known in thisfield can be used, such as flow stirring and stirring utilizing theshearing force by means of a reversal agitator or a dissolver. Also, astirring method utilizing the shearing force with the bottom surface ofa vessel, such as magnetic stirrer, can be advantageously used.

The recording paper and recording film for use in the image recordingmethod of the present invention are described below. The support whichcan be used for the recording paper or film is produced, for example,from a chemical pulp such as LBKP and NBKP, a mechanical pulp such asGP, PGW, RMP, TMP, CTMP, CMP and CGP, or a waste paper pulp such as DIP,by mixing, if desired, conventionally known additives such as pigment,binder, sizing agent, fixing agent, cation agent and paper strengthincreasing agent, and then sheeting the mixture by using various devicessuch as Fourdrinier paper machine and cylinder paper machine. Other thanthese supports, synthetic paper or plastic film sheet may be used as thesupport. The thickness of the support is preferably from 10 to 250 μmand the basis weight is preferably from 10 to 250 g/m².

An image-receiving layer and a backcoat layer may be provided on thesupport as it is to produce an image-receiving material, or afterproviding a size press or an anchor coat layer by using starch,polyvinyl alcohol or the like, an image-receiving layer and a backcoatlayer may be provided to produce an image-receiving material. Thesupport may be further subjected to a flattening treatment by acalendering device such as machine calender, TG calender and softcalender.

In the present invention, the support is preferably paper or plasticfilm of which both surfaces are laminated with polyolefin (for example,polyethylene, polystyrene, polyethylene terephthalate, polybutene or acopolymer thereof). In the polyolefin, a white pigment (for example,titanium oxide or zinc oxide) or a tinting dye (for example, cobaltblue, ultramarine or neodymium oxide) is preferably added.

The image-receiving layer provided on the support contains a porousmaterial and an aqueous binder. Also, the image-receiving layerpreferably contains a pigment and the pigment is preferably a whitepigment. Examples of the white pigment include inorganic white pigmentssuch as calcium carbonate, kaolin, talc, clay, diatomaceous earth,synthetic amorphous silica, aluminum silicate, magnesium silicate,calcium silicate, aluminum hydroxide, alumina, lithopone, zeolite,barium sulfate, calcium sulfate, titanium dioxide, zinc sulfide and zinccarbonate, and organic pigments such as styrene-base pigment, acryl-basepigment, urea resin and melamine resin. Among these, porous inorganicwhite pigments are preferred, and synthetic amorphous silica and thelike having a large pore area are more preferred. The syntheticamorphous silica may be either a silicic acid anhydride obtained by adry production process or a silicic acid hydrate obtained by a wetproduction process. These pigments may be used in combination of two ormore thereof.

Examples of the aqueous binder contained in the image-receiving layerinclude water-soluble polymers such as polyvinyl alcohol,silanol-modified polyvinyl alcohol, starch, cationized starch, casein,gelatin, carboxymethyl cellulose, hydroxyethyl cellulose,polyvinylpyrrolidone, polyalkylene oxide and polyalkylene oxidederivative, and water-dispersible polymers such as styrene butadienelatex and acryl emulsion. These aqueous binders can be used individuallyor in combination of two or more thereof. Among these, polyvinyl alcoholand silanol-modified polyvinyl alcohol are preferred in the presentinvention in view of adhesion to the pigment and peeling resistance ofthe image-receiving layer.

The image-receiving layer may contain a mordant, a water-proofing agent,a light fastness enhancer, a surfactant, a hardening agent and otheradditives in addition to the pigment and aqueous binder.

The mordant added to the image-receiving layer is preferably immobilizedand for this purpose, a polymer mordant is preferably used.

The polymer mordant is described in JP-A-48-28325, JP-A-54-74430,JP-A-54-124726, JP-A-55-22766, JP-A-55-142339, JP-A-60-23850,JP-A-60-23851, JP-A-60-23852, JP-A-60-23853, JP-A-60-57836,JP-A-60-60643, JP-A-60-118834, JP-A-60-122940, JP-A-60-122941,JP-A-60-122942, JP-A-60-235134, JP-A-1-161236 and U.S. Pat. Nos.2,484,430, 2,548,564, 3,148,061, 3,309,690, 4,115,124, 4,124,386,4,193,800, 4,273,853, 4,282,305 and 4,450,224. An image-receivingmaterial containing the polymer mordant described in JP-A-1-161236(pages 212 to 215) is particularly preferred. When the polymer mordantdescribed in this patent publication is used, an image having excellentimage quality can be obtained and at the same time, the light fastnessof the image is improved.

The water-proofing agent is effective for obtaining a water-resistantimage. The water-proofing agent is preferably a cationic resin. Examplesof the cationic resin include polyamidopolyamine epichlorohydrin,polyethyleneimine, polyaminesulfone, poly-dimethyldiallylammoniumchloride, cationic polyacrylamide and colloidal silica. Among thesecationic resins, polyamidopolyamine epichlorohydrin is preferred. Thecontent of the cationic resin is preferably from 1 to 15 mass %, morepreferably from 3 to 10 mass %, based on the entire solid content of theink-receiving layer.

Examples of the light fastness enhancer include zinc sulfate, zincoxide, hindered amine-base antioxidant and benzotriazole-baseultraviolet absorbent such as benzophenone. Among these, zinc sulfate ispreferred.

The surfactant functions as a coating aid, a releasability improver, aslipperiness improver or an antistatic agent. This surfactant isdescribed in JP-A-62-173463 and JP-A-62-183457.

Instead of the surfactant, an organofluoro compound may be used. Theorganofluoro compound is preferably hydrophobic. Examples of theorganofluoro compound include fluorine-containing surfactants, oilyfluorine-base compounds (for example, fluorine oil) and solid fluorinecompound resins (for example, ethylene tetrafluoride resin). Theorganofluoro compound is described in JP-B-57-9053 (columns 8 to 17),JP-A-61-20994 and JP-A-62-135826.

As the hardening agent, for example, the materials described inJP-A-1-161236 (page 222) can be used.

Other examples of the additive added to the image-receiving layerinclude a pigment dispersant, a thickener, a defoaming agent, a dye, afluorescent brightening agent, an antiseptic, a pH adjusting agent, amatting agent and a hardening agent. The image-receiving layer may becomposed of one layer or two layers.

In the recording paper or film, a backcoat layer may also be provided.Examples of the component which can be added to this layer include awhite pigment, an aqueous binder and other components.

Examples of the white pigment contained in the backcoat layer includewhite inorganic pigments such as precipitated calcium carbonate, heavycalcium carbonate, kaolin, talc, calcium sulfate, barium sulfate,titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white,aluminum silicate, diatomaceous earth, calcium silicate, magnesiumsilicate, synthetic amorphous silica, colloidal silica, colloidalalumina, pseudo-boehmite, aluminum hydroxide, alumina, lithopone,zeolite, hydrolyzed halloysite, magnesium carbonate and magnesiumhydroxide, and organic pigments such as styrene-base plastic pigment,acryl-base plastic pigment, polyethylene, microcapsule, urea resin andmelamine resin.

Examples of the aqueous binder contained in the backcoat layer includewater-soluble polymers such as styrene/maleate copolymer,styrene/acrylate copolymer, polyvinyl alcohol, silanol-modifiedpolyvinyl alcohol, starch, cationized starch, casein, gelatin,carboxymethyl cellulose, hydroxyethyl cellulose andpolyvinylpyrrolidone, and water-dispersible polymers such as styrenebutadiene latex and acryl emulsion. Other examples of the componentcontained in the backcoat layer include a defoaming agent, a foaminhibitor, a dye, a fluorescent brightening agent, an antiseptic and awater-proofing agent.

In a constituent layer (including the back layer) of the inkjetrecording paper or film, a polymer fine particle dispersion may beadded. The polymer fine particle dispersion is used for the purpose ofimproving film properties, for example, stabilizing the dimension andpreventing the curling, adhesion or film cracking. The polymer fineparticle dispersion is described in JP-A-62-245258, JP-A-62-1316648 andJP-A-62-110066. When a polymer fine particle dispersion having a lowglass transition temperature (40° C. or less) is added to a layercontaining a mordant, the layer can be prevented from cracking orcurling. The curling can be prevented also by adding a polymer fineparticle dispersion having a high glass transition temperature to theback layer.

The present invention is not limited in the inkjet recording system andused for a known system, for example, an electric charge control systemof jetting out the ink by utilizing the electrostatic induction force, adrop-on-demand system (pressure pulse system) utilizing an oscillationpressure of a piezoelectric element, an acoustic inkjet system ofconverting electric signals into acoustic beams, irradiating the beamson the ink and jetting out the ink by utilizing the radiation pressure,and a thermal inkjet (bubble jet) system of heating the ink to form abubble and utilizing the pressure generated.

The inkjet recording system includes a system of ejecting a large numberof small-volume ink droplets of a so-called photo ink having a lowconcentration, a system of improving the image quality by using aplurality of inks having substantially the same color hue but differingin the concentration, and a system using a colorless transparent ink.

The inkjet recording ink of the present invention can also be used foruses other than the inkjet recording, such as a material for displayimage, an image-forming material for interior decoration, and animage-forming material for outdoor decoration.

The material for display image indicates various materials such asposter, wallpaper, ornamental goods (e.g., ornament, doll), handbill forcommercial advertisement, wrapping paper, wrapping material, paper bag,vinyl bag, package material, billboard, image drawn on or attached tothe side face of traffic (e.g., automobile, bus, electric car), andclothing with a logo. In the case of using the dye of the presentinvention as a material for forming a display image, the image includesnot only a strict image but also all patterns by a dye, which can beperceived by a human, such as abstract design, letter and geometricalpattern.

The material for interior decoration indicates various materials such aswallpaper, ornamental goods (e.g., ornament, doll), luminaire member,furniture member and design member of floor or ceiling. In the case ofusing the dye of the present invention as a material for forming animage, the image includes not only a strict image but also all patternsby a dye, which can be perceived by a human, such as abstract design,letter and geometrical pattern.

The material for outdoor decoration indicates various materials such aswall material, roofing material, billboard, gardening material, outdoorornamental goods (e.g., ornament, doll) and outdoor luminaire member. Inthe case of using the dye of the present invention as a material forforming an image, the image includes not only a strict image but alsoall patterns by a dye, which can be perceived by a human, such asabstract design, letter and geometrical pattern.

In these uses, examples of the medium on which the pattern is formedinclude various materials such as paper, fiber, cloth (includingnon-woven fabric), plastic, metal and ceramic. Examples of the dyeingform include mordanting, printing and fixing of a coloring material inthe form of a reactive dye having introduced thereinto a reactive group.Among these, preferred is dyeing by mordanting.

EXAMPLES

The present invention is described below by referring to Examples, butthe present invention is not limited thereto.

Example 1

Deionized water was added to the following components to make 1 literand the resulting solution was stirred for 1 hour under heating at 30 to40° C. and then filtered under reduced pressure through a microfilterhaving an average pore size of 0.25 μm to prepare a light magenta inksolution (LM-101).

[Formulation of Light Magenta Ink (LM-101)]

(Solid Contents) Magenta Dye (a-36) of the present  7.5 g/literinvention Urea  37 g/liter (Liquid Components) Diethylene glycol (DEG)140 g/liter Glycerin (GR) 120 g/liter Triethylene glycol monobutyl ether(TGB) 120 g/liter Triethanolamine (TEA)  6.9 g/liter Surfynol STG (SW) 10 g/liter

Also, a magenta ink solution (M-101) was prepared by increasing MagentaDye (a-36) to 23 g in the formulation above.

[Formulation of Magenta Ink (M-101)]

(Solid Contents) Magenta Dye (a-36) of the present  23 g/liter inventionUrea  37 g/liter (Liquid Components) Diethylene glycol (DEG) 140 g/literGlycerin (GR) 120 g/liter Triethylene glycol monobutyl ether (TGB) 120g/liter Triethanolamine (TEA)  6.9 g/liter Surfynol STG (SW)  10 g/liter

Light magenta inks and magenta inks each having thoroughly the samecomposition as the ink (LM-101) or (M-101) except for changing the kindof dye as shown in Table A below were produced.

TABLE A Light Magenta Magenta Dye Dye No. 1 (Comparative Example) a-36a-36 No. 2 (Comparative Example) D-1 D-1 No. 3 (Comparative Example) D-2D-2 No. 4 (Invention) a-36 D-1 No. 5 (Invention) a-36 D-2 No. 6(Invention) a-36   5 g a-36 15 g a-15 2.5 g a-15  8 g No. 7 (Invention)a-36 2.5 g a-36  8 g a-15   5 g a-15 15 g No. 8 (Invention) a-36   5 ga-36 15 g D-1   4 g D-1 12 g No. 9 (Invention) a-36   5 g a-36 15 g D-2  5 g D-1 15 g No. 10 (Invention) a-36 a-15 D-1:

D-2:

These inks each was filled in the magenta ink-light magenta inkcartridge of Inkjet Printer PM-950C (manufactured by Seiko EpsonCorporation) and by using the inks of PM-950C for other colors, imagesdiffering in the density were printed. The image-receiving sheet wherethe image was printed was inkjet paper Photo Gloss Paper EX produced byFuji Photo Film Co., Ltd. The image obtained was evaluated on theejection property of ink and image fastness.

(Evaluation Test)

<Evaluation Methods and Evaluation Criteria>

1) Ejection Stability

As for the ejection stability, cartridges were set in the printer andafter confirming the ejection of ink from all nozzles, the image wasoutput on 20 sheets of A4-size paper and rated based on the followingcriteria:

A: Printing was not disordered from start to end of printing.

B: Printing was disordered in some outputs.

C: Printing was disordered from start to end of printing.

This test was performed immediately after the filling of ink (ejectionproperty A) and after the ink cartridge was stored for 2 weeks under theconditions of 40° C. and 80% RH (ejection property B).

2) Image Preservability

As for the image preservability, a magenta solid image printed samplewas prepared and subjected to the following evaluations.

(1) Light Fastness

The image density Ci immediately after printing was measured by X-Rite310 and after the image was irradiated with xenon light (85,000 lx) for10 days by using a weather meter manufactured by Atlas, the imagedensity Cf was again measured. Then, the dye residual ratio (Cf/Ci*100)was determined and evaluated. The dye residual ratio was evaluated atthree points having a reflection density of 1, 1.5 and 2. The sample wasrated A when the dye residual ratio was 70% or more at any density,rated B when less than 70% at two points, and rated C when less than 70%at all points.

(2) Heat Fastness

The density was measured by X-Rite 310 before and after the sample wasstored for 10 days under the conditions of 80° C. and 15% RH, and thedye residual ratio was determined and evaluated. The dye residual ratiowas evaluated at three points having a reflection density of 1, 1.5 and2. The sample was rated A when the dye residual ratio was 90% or more atany density, rated B when less than 90% at two points, and rated C whenless than 90% at all points.

(3) Ozone Resistance

The photo gloss paper having formed thereon the image was left standingfor 7 days in a box set to an ozone gas concentration of 0.5 ppm and theimage density before and after standing in the ozone gas atmosphere wasmeasured by a reflection densitometer (X-Rite 310TR) and evaluated interms of the coloring matter residual ratio. The reflection density wasmeasured at three points of 1, 1.5 and 2.0. The ozone gas concentrationin the box was set by using an ozone gas monitor (Model OZG-EM-01)manufactured by APPLICS.

The sample was rated on a three-stage scale, namely, rated A when thecoloring matter residual ratio was 80% or more at any density, rated Bwhen less than 80% at one or two point(s), and rated C when less than70% at all points.

3) Blurring of Image

As for the blurring of the image under high-humidity conditions, aprinting pattern where four magenta square patterns each in a size of 3cm×3 cm were arrayed to form a two-line and two-column table shape witha 1-mm white clearance between respective square patterns was preparedand after this image sample was stored under conditions of 25° C. and90% RH for 72 hours, the bleeding of magenta dye in the white clearancewas observed. The sample was rated A when the increase of magentadensity in the white clearance based on the density immediately afterprinting was less than 0.01 as measured by a magenta filter of Status A,rated B when from 0.01 to 0.05, and rated C when more than 0.05.

The results obtained are shown in Table B below.

TABLE B Ejection Light Heat O₃ Property Fastness Fastness ResistanceBlurring Genuine ink of A C B C B EPSON (PM-950C) No. 1 A A A A C(Comparative Example) No. 2 A B A C C (Comparative Example) No. 3 A B AC C (Comparative Example) No. 4 (Invention) A A A A A No. 5 (Invention)A A A A A No. 6 (Invention) A A A A A No. 7 (Invention) A A A A A No. 8(Invention) A A A A A No. 9 (Invention) A A A A A No. 10 (Invention) A AA A A

As seen from the results in Table B, the systems using the ink set ofthe present invention were satisfied in ejection stability and infastness and blurring of image and excellent as compared withComparative Examples. These results clearly verify the effects of thepresent invention.

Example 2

Deionized water was added to the following components to make 1 literand the resulting solution was stirred for 1 hour under heating at 30 to40° C. and then filtered under reduced pressure through a microfilterhaving an average pore size of 0.25 μm to prepare a light magenta inksolution (LM-102).

[Formulation of Light Magenta Ink (LM-102)]

(Solid Contents) Magenta Dye (a-36) of the present  7.5 g/literinvention Urea  37 g/liter (Liquid Components) Diethylene glycol (DEG)150 g/liter Glycerin (GR) 120 g/liter Triethylene glycol monobutyl ether(TGB) 120 g/liter Triethanolamine (TEA)  6.9 g/liter Surfynol STG (SW) 10 g/liter

Also, a magenta ink solution (M-102) was prepared by increasing MagentaDye (a-36) to 23 g in the formulation above.

[Formulation of Magenta Ink (M-102)]

(Solid Contents) Magenta Dye (a-36) of the present  23 g/liter inventionUrea  37 g/liter (Liquid Components) Diethylene glycol (DEG) 150 g/literGlycerin (GR) 120 g/liter Triethylene glycol monobutyl ether (TGB) 120g/liter Triethanolamine (TEA)  6.9 g/liter Surfynol STG (SW)  10 g/liter

Levels changed in the ink composition of the light magenta ink (LM-102)or magenta ink (M-102) as shown in Table C were produced.

TABLE C Light Magenta Ink Magenta Ink No. 1 (Comparative Example) LM-101M-101 No. 2 (Comparative Example) light magenta ink magenta ink of ofPM-5000C PM-5000C No. 3 (Comparative Example) light magenta ink magentaink of of PM-950C PM-950C No. 4 (Invention) LM-101 magenta ink ofPM-950C No. 5 (Invention) light magenta ink M-101 of PM-5000C No. 6(Invention) LM-101 magenta ink of PM-5000C PM-5000C is a pigment ink andPM-950C is a water-soluble dye ink.

These inks each was filled in the magenta ink or light magenta inkcartridge of Inkjet Printer PM-950C (manufactured by Seiko EpsonCorporation) and by using the inks of PM-950C for other colors, eachcolor image differing in the density was printed. The image-receivingsheet where the image was printed was inkjet paper Photo Gloss Paper EXproduced by Fuji Photo Film Co., Ltd. The image obtained was evaluatedon the ejection property of ink and image fastness.

(Evaluation Test)

1) Ejection Stability

The test was performed by the method described in Example 1.

2) Image Preservability

The test was performed by the method described in Example 1.

3) Transparency of Image in High-Density Area

In the evaluation of blurring of image, the transparency of image in thehigh-density area was evaluated as a property related to blurring. Thatis, the samples were classified into A to C ranks by the evaluation withan eye (A: good, B: normal, C: bad).

The results obtained are shown in Table D below.

TABLE D Ejection Light Heat O₃ Trans- Property Fastness FastnessResistance parency No. 1 A B A A A (Comparative Example) No. 2 A A A A C(Comparative Example) No. 3 A C A C A (Comparative Example) No. 4(Invention) A B A B A No. 5 (Invention) A A A A A No. 6 (Invention) A AA A B

As seen from the results in Table D, the systems using the ink set ofthe present invention, where two inks were divided into light magentaink and magenta ink, were satisfied in ejection stability and surpassedComparative Examples in view of fastness and transparency of image (morespecifically, Sample No. 4 of the invention was excellent in lightfastness and transparency as compared with corresponding Sample No. 3 ofComparative Example, Sample Nos. 5 and 6 of the invention were excellentin transparency as compared with corresponding Sample No. 2 ofComparative Example, and Sample No. 6 was excellent in light fastness ascompared with Sample No. 1 which is another objective of comparison anddespite slightly inferior transparency, rated superior overall). It isalso seen that the transparency was more excellent when a pigment inkwas used as the light magenta ink. These results clearly verify theeffects of the present invention.

Example 3

Deionized water was added to the following components to make 1 literand the resulting solution was stirred for 1 hour under heating at 30 to40° C. and then filtered under reduced pressure through a microfilterhaving an average pore size of 0.25 μm to prepare a light cyan inksolution (LC-101).

[Formulation of Light Cyan Ink (LC-101)]

(Solid Contents) Cyan Dye (154) of the present invention 17.5 g/literProxel  3.5 g/liter (Liquid Components) Diethylene glycol  150 g/literGlycerin  130 g/liter Triethylene glycol monobutyl ether  130 g/literTriethanolamine  6.9 g/liter Surfynol STG (SW: nonionic surfactant)   10g/liter

Also, Cyan Ink Solution (C-101) was prepared by increasing Cyan Dye(154) to 68 g in the formulation above.

[Formulation of Cyan Ink (C-101)]

(Solid Contents) Cyan Dye (154) of the present invention  68 g/literProxel  3.5 g/liter (Liquid Components) Diethylene glycol 150 g/literGlycerin 130 g/liter Triethylene glycol monobutyl ether 130 g/literTriethanolamine  6.9 g/liter Surfynol STG  10 g/liter

Levels changed in the ink composition of the light cyan ink (LC-101) orcyan ink (C-101) as shown below were produced.

TABLE E Light Cyan Ink Cyan Ink No. 1 (Comparative Example) LC-101 C-101No. 2 (Comparative Example) light cyan ink of cyan ink of PM- PM-5000C5000C No. 3 (Comparative Example) light cyan ink of cyan ink of PM-PM-950C 950C No. 4 (Invention) LC-101 cyan ink of PM- 950C No. 5(Invention) light cyan ink of C-101 PM-5000C No. 6 (Invention) LC-101cyan ink of PM- 5000C PM-5000C is a pigment ink and PM-950C is awater-soluble dye ink.

These inks each was filled in the cyan ink•light cyan ink cartridge ofInkjet Printer PM-950C (manufactured by Seiko Epson Corporation) and byusing the inks of PM-950C for other colors, a cyan monochromatic imagewas printed. The image-receiving sheet where the image was printed wasinkjet paper Photo Gloss Paper EX produced by Fuji Photo Film Co., Ltd.The image obtained was evaluated on the ejection property and imagefastness.

(Evaluation Test)

1) Ejection Stability

The test was performed by the method described in Example 1.

2) Image Preservability

The test was performed by the method described in Example 1.

3) Letter Grade of Image

The blurring of image was evaluated by the letter grade which is animage property reflecting the blurring of image. More specifically,letters

and

were printed in 14-point size and 50 characters were printed for eachletter. The linear portion of each character was observed through amicroscope and rated according to the following criteria.

A: The ink in the linear part was protruded in 5 characters out of 100characters in total.

B: The ink in the linear part was protruded in 6 to 40 characters out of100 characters in total.

C: The ink in the linear part was protruded in 41 or more characters outof 100 characters in total.

4) Transparency of Image

The transparency of image, which is another property reflecting theblurring of image, was also evaluated. The evaluation was performed bythe method described in Example 2.

The results obtained are shown in Table F below.

TABLE F Ejection Light Heat O₃ Trans- Property Fastness FastnessResistance parency No. 1 A B A A A (Comparative Example) No. 2 A A A A C(Comparative Example) No. 3 A C A C A (Comparative Example) No. 4(Invention) A B A B A No. 5 (Invention) A A A A A No. 6 (Invention) A AA A B

As seen from the results in Table F, the systems using the ink set ofthe present invention were satisfied in ejection stability and superiorto Comparative Examples in view of image preservability and blurring ofimage (letter grade and transparency) (more specifically, Sample No. 4of the invention was excellent in light fastness and transparency ascompared with corresponding Sample No. 3 of Comparative Example, SampleNos. 5 and 6 of the invention were excellent in transparency as comparedwith corresponding Sample No. 2 of Comparative Example, and Sample No. 6was excellent in light fastness as compared with Sample No. 1 which isanother objective of comparison and despite slightly inferiortransparency, rated superior overall). It is also seen that thetransparency was more excellent when a pigment ink was used as the lightcyan ink. These results clearly verify the effects of the presentinvention.

Example 4

Light cyan inks and cyan inks each having thoroughly the samecomposition as the light cyan ink (LC-101) or cyan ink (C-101) ofExample 3 except for changing the kind of dye as shown below wereproduced.

TABLE G Light Magenta Magenta Dye Dye No. 1 (Comparative Example) a-36a-36 No. 2 (Comparative Example) D-1 D-1 No. 3 (Comparative Example) D-2D-2 No. 4 (Invention) a-36 D-1 No. 5 (Invention) a-36 D-2 No. 6(Invention) a-36 5 g a-36 15 g a-15 2.5 g   a-15  8 g No. 7 (Invention)a-36 2.5 g   a-36  8 g a-15 5 g a-15 15 g No. 8 (Invention) a-36 5 ga-36 15 g D-1 4 g D-1 12 g No. 9 (Invention) a-36 5 g a-36 15 g D-2 5 gD-1 15 g No. 10 (Invention) a-36 a-15

These inks each was filled in the cyan ink•light cyan ink cartridge ofInkjet Printer PM-950C (manufactured by Seiko Epson Corporation) and byusing the inks of PM-950C for other colors, a cyan monochromatic imagewas printed.

The image-receiving sheet where the image was printed was inkjet paperPhoto Gloss Paper EX produced by Fuji Photo Film Co., Ltd. The imageobtained was evaluated on the ejection property and image fastness.

(Evaluation Test)

1) Ejection Stability

The test was performed by the method described in Example 1.

2) Image Preservability

The test was performed by the method described in Example 1.

3) Blurring of Image Under High-Humidity Conditions

The test was performed by the method described in Example 1.

The results obtained are shown in Table H below.

TABLE H Ejection Light Heat O₃ Property Fastness Fastness ResistanceBlurring Genuine ink of A C B C B EPSON (PM-950C) No. 1 A A A A C(Comparative Example) No. 2 A B A C C (Comparative Example) No. 3 A B AC C (Comparative Example) No. 4 (Invention) A A A A A No. 5 (Invention)A A A A A No. 6 (Invention) A A A A A No. 7 (Invention) A A A A A No. 8(Invention) A A A A A No. 9 (Invention) A A A A A

As seen from the results in Table H, the systems using the ink set ofthe present invention were satisfied in ejection stability, imagepreservability (e.g., fastness) and blurring of image and superior toComparative Examples. These results clearly verify the effects of thepresent invention.

INDUSTRIAL APPLICABILITY

As described in the foregoing pages, by the ink (or ink set) of thepresent invention using two coloring materials sharing the mainabsorption region, an inkjet recorded image excellent in weatherresistance (image preservability) and having less blurring of imagedrawn can be obtained and moreover, inkjet recording with high ejectionstability can be performed.

1. An inkjet recording ink, comprising an aqueous medium havingdissolved therein at least two water soluble coloring materials sharingone spectral absorption region selected from a region of 500 to 580 nmand a region of 580 to 680 nm as a main absorption region in the aqueousmedium, wherein at least one of said water soluble coloring materialssharing the region of 500 to 580 nm as a main absorption region is anazo dye having a chromophore represented by the formula: (heterocyclicring A)-N═N-(heterocyclic ring B), provided that the heterocyclic ring Aand the heterocyclic B may have the same structure.
 2. The inkjetrecording ink as claimed in claim 1, wherein at least two of said watersoluble coloring materials sharing one spectral absorption regionselected from a region of 500 to 580 nm and a region of 580 to 680 nm asa main absorption region in the aqueous medium are dissolved in a singleaqueous medium.
 3. The inkjet recording ink as claimed in claim 1,wherein at least two of said water soluble coloring materials sharingone spectral absorption region selected from a region of 500 to 580 nmand a region of 580 to 680 nm as a main absorption region in the aqueousmedium are separately dissolved in multiple aqueous mediums.
 4. Theinkjet recording ink as claimed in claim 1, wherein the main absorptionregion shared by at least two of said water soluble coloring materialsin the aqueous medium is the region of 500 to 580 nm.
 5. The inkjetrecording ink as claimed in claim 1, wherein the azo dye having achromophore represented by the formula: (heterocyclic ringA)-N═N-(heterocyclic ring B), is a coloring material having an oxidationpotential nobler than 0.7 V (vs SCE).
 6. The inkjet recording ink asclaimed in claim 1, wherein said azo dye is a dye represented by thefollowing formula (1): Formula (1):

wherein A represents a 5-membered heterocyclic group; B¹ and B² eachrepresents ═CR¹— or —CR²═ or either one of B¹ and B² represents anitrogen atom and other represents ═CR¹— or —CR²═; R⁵ and R⁶ eachindependently represents a hydrogen atom or a substituent, saidsubstituent is an aliphatic group, an aromatic group, a heterocyclicgroup, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group,a carbamoyl group, an alkylsulfonyl group, an arylsulfonyl group or asulfamoyl group, and hydrogen atom of each substituent may besubstituted; G, R¹ and R² each independently represents a hydrogen atomor a substituent, said substituent is a halogen atom, an aliphaticgroup, an aromatic group, a heterocyclic group, a cyano group, acarboxyl group, a carbamoyl group, an alkoxycarbonyl group, anaryloxycarbonyl group, a heterocyclic oxycarbonyl group, an acyl group,a hydroxy group, an alkoxy group, an aryloxy group, a heterocyclic oxygroup, a silyloxy group, an acyloxy group, a carbamoyloxy group, analkoxycarbonyloxy group, an aryloxycarbonyloxy group, an amino group, anacylamino group, a ureido group, a sulfamoylamino group, analkoxycarbonylamino group, an aryloxycarbonylamino group, analkylsulfonylamino group, an arylsulfonylamino group, a heterocyclicsulfonylamino group, a nitro group, an alkylthio group, an arylthiogroup, a heterocyclic thio group, an alkylsulfonyl group, anarylsulfonyl group, a heterocyclic sulfonyl group, an alkylsulfinylgroup, an arylsulfinyl group, a heterocyclic sulfinyl group, a sulfamoylgroup or a sulfo group, and hydrogen atom of each substituent may besubstituted; and R¹ and R^(5,) or R⁵ and R⁶ may combine to form a 5- or6-membered ring.
 7. The inkjet recording ink as claimed in claim 6,wherein said at least two water soluble coloring materials sharing themain absorption region both are the dye represented by formula (1). 8.The inkjet recording ink as claimed in claim 1, wherein the mainabsorption region shared by at least two of said water soluble coloringmaterials in the aqueous medium is the region of 580 to 680 nm.
 9. Theinkjet recording ink as claimed in claim 8, wherein at least one of saidwater soluble coloring materials sharing the region of 580 to 680 nm asa main absorption region is a dye represented by the following formula(I):

wherein X_(1,) X_(2,) X₃ and X₄ each independently represents —SO-Z,—SO₂-Z, —SO₂NR₁R₂, a sulfo group, —CONR₁R₂ or —CO₂R₁, in which Zrepresents a substituted or unsubstituted alkyl group, a substituted orunsubstituted cycloalkyl group, a substituted or unsubstituted alkenylgroup, a substituted or unsubstituted aralkyl group, a substituted orunsubstituted aryl group, or a substituted or unsubstituted heterocyclicgroup, and R₁ and R₂ each independently represents a hydrogen atom, asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedcycloalkyl group, a substituted or unsubstituted alkenyl group, asubstituted or unsubstituted aralkyl group, a substituted orunsubstituted aryl group, or a substituted or unsubstituted heterocyclicgroup, provided that when a plurality of Zs are present, these may besame or different, Y_(1,) Y_(2,) Y₃ and Y₄ each independently representsa monovalent substituent, provided that when a plurality of X₁s, X₂s,X₃s, X₄s, Y₁s, Y₂s, Y₃s or Y₄s are present, these may be same ordifferent, a₁ to a₄ and b₁ to b₄ represent a number of substituents X₁to X₄ and Y₁ to Y_(4,) respectively, a₁ to a₄ each independentlyrepresents an integer of 0 to 4 but all are not 0 at a same time, b₁ tob₄ each independently represents an integer of 0 to 4, and M representsa hydrogen atom, a metal atom or an oxide, hydroxide or halide thereof.10. The inkjet recording ink as claimed in claim 9, wherein the dyerepresented by formula (I) is a dye represented by the following formula(II):

wherein X₁₁ to X_(14,) Y₁₁ to Y₁₈ and M have same meanings as X₁ toX_(4,) Y₁ to Y₄ and M in formula (I), respectively, and a₁₁ to a₁₄ eachindependently represents an integer of 1 or
 2. 11. The inkjet recordingink as claimed in claim 9, wherein the dye represented by formula (I) isa coloring material having an oxidation potential nobler than 0.7 V (vsSCE).
 12. The inkjet recording ink as claimed in any one of claims 8 to10, wherein at least one dye represented by formula (I) and at least onedye having a structure different from said dye are dissolved in anaqueous medium.
 13. The inkiet recording ink as claimed in claim 8,wherein at least two dyes represented by formula (I) are dissolved in anaqueous medium.
 14. An inkjet recording method comprising using the inkclaimed in claim
 1. 15. The inkjet recording method as claimed in claim14, which uses an ink set comprising multiple aqueous mediums havingseparately dissolved therein at least two water soluble coloringmaterials sharing one spectral absorption region selected from a regionof 500 to 580 nm and a region of 580 to 680 nm as a main absorptionregion in the aqueous medium, wherein an inkjet recording ink comprisingan aqueous medium having dissolved therein at least one dye representedby formula (I) and an inkiet recording ink comprising an aqueous mediumhaving dissolved therein at least one coloring material differing in astructure from said dye and sharing the main absorption region with saiddye are used as a combined set.
 16. The inkjet recording method asclaimed in claim 14, which uses an ink comprising an aqueous mediumhaving dissolved therein at least two water soluble coloring materialssharing one spectral absorption region selected from a region of 500 to580 nm and a region of 580 to 680 nm as a main absorption region in theaqueous medium, wherein in the inkjet recording ink used, at least onedye represented by formula (1) and at least one dye differing instructure from said dye and sharing the main absorption region with saiddye are dissolved in the same aqueous medium.
 17. The inkjet recordingmethod as claimed in any one of claims 14 to 16, wherein an image isrecorded by ejecting ink droplets according to recording signals on animage-receiving material comprising a support having thereon animage-receiving layer containing an inorganic white pigment particle.18. The inkiet recording method as claimed in claim 17, wherein theimage-receiving layer comprises an inorganic white pigment particle andat least one aqueous binder selected from polyvinyl alcohol,silanol-modified polyvinyl alcohol, starch, cationized starch, gelatin,carboxyalkyl cellulose, casein and polyvinylpyrrolidone.